All of the familiar Office toolbars and menus have been replaced by the Ribbon, a super toolbar divided into seven tabs grouped by commands.

So, when Microsoft makes significant changes to Office, it’s a big deal. And the latest version of the software suite, called Office 2007, due out Jan. 30, is a radical revision, the most dramatic overhaul in a decade or more.

I don’t use the word “radical” lightly. The entire user interface, the way you do things in these familiar old programs, has been thrown out and replaced with something new. In Word, Excel and PowerPoint, all of the menus are gone — every one. None of the familiar toolbars have survived, either. In their place is a wide, tabbed band of icons at the top of the screen called the Ribbon. And there is no option to go back to the classic interface.

In Outlook, the Ribbon hasn’t kicked out the menus and toolbars in the program’s main screens, but if you compose an email, or set up a new contact or appointment, you’ll see it.

As if this weren’t enough, Microsoft has also changed the standard file format for Office files. Older versions of Office, on both Windows and Macintosh computers, won’t be able to read these new file types without special conversion software. The new version can, however, read files created in the older versions, on both Windows and Mac, without any conversion software.

These changes in Office, while much less publicized, are far bolder and more important than the mostly cosmetic user interface changes in the highly hyped new version of Windows, called Vista, which comes out on the same day.

After months of working with the Ribbon and other new features of Office, I believe they are an improvement. They replace years of confusing accretions with a logical layout of commands and functions. They add easy and elegant new options for making documents look good. And they make it much simpler to find many of the 1,500 commands that Office offers, but had buried in the past.

In the new Word, above, the round Office button replaces the file menu in the old Word, below, which had commands spread across many menus and toolbars. New features include contextual spell checking and translations into other languages.

So, Microsoft deserves credit for being bold and creative in designing Office 2007. It has taken a good product and made it better and fresher.

But there is a big downside to this gutsy redesign: It requires a steep learning curve that many people might rather avoid. In my own tests, I was cursing the program for weeks because I couldn’t find familiar functions and commands, even though Microsoft provides lots of help and guidance.

It’s as if Toyota decided to switch the position of choices on the automobile shift lever, or Motorola decided to rearrange the buttons on the cellphone key pad. Even if the companies could conclusively show that the changes made life easier, many people would be annoyed at best, and furious at worst.

In the case of the new Office, I think the changes are most beneficial for users concerned with the layout and design of documents. The commands that are now better arranged and easier to find are mainly those that relate to formatting, layout, graphics and design.

By contrast, basic composition and editing are aided by the new design either very little or not at all. If you mostly compose plain Word documents, simple presentations and plain spreadsheets, the new design may not be worth the effort to master it, and you might want to stick with an older version of Office. People with the new version will still be able to read your documents and you can get free conversion software so you can read new files.

The old Word.

The other group of users who might be better off skipping Office 2007 are power users who know many commands and have customized their menus and toolbars heavily. The new Office is much less customizable.

In fact, you can’t customize the Ribbon. To add favorite commands, all you can do is customize a tiny minitoolbar in the upper left corner of the screen, called the Quick Access Toolbar.

For people who mostly control Office via keyboard commands, and rarely use menus and toolbars, all of the basic keyboard commands are the same.

There are other nice additions. In Word, Outlook and PowerPoint, there is now contextual spell checking, which points to a wrong word, even if the spelling is in the dictionary. For example, if you type “their” instead of “they’re,” Office catches the mistake. It really works.

In addition, throughout Office, there is a function that translates a word or sentence into other languages. In PowerPoint and Excel, there are new, better-looking graphics for charts and tables.

And all the programs have Live Preview, a feature long offered by WordPerfect, which shows a formatting change before you commit to it. You can see what a new font or style would look like by hovering over the choice with the mouse.

Outlook, the least changed of the programs, finally catches up to other email programs with a fast search capability and the ability to preview attachments without opening them.

But the Ribbon is the biggest change. It’s essentially a super toolbar divided into seven logical tabs, which attempt to group similar commands. Each tab brings up a new version of the Ribbon. Common file-handling functions like Open, Save and Print aren’t on the Ribbon. They are accessed by clicking on a big round icon at the upper left called the Office Button, which is roughly the equivalent of the old File menu. Clicking the Office Button also displays a much larger and longer list of recently opened files than the old File menu did, and you can even permanently “pin” files to this list.

There’s no doubt that some functions are quicker and easier in the new interface. Narrowing the margins in a Word document now takes as few as three clicks, compared with up to 14 clicks and keystrokes in old versions.

Applying styles to a Word document is also easier. The Ribbon has a bunch of them in the Home tab, illustrated with big square icons that show what they look like, and you just can just click and apply the one you want.

But some less-common tasks are harder without the old menus and tool bars, such as adding a new word to the Auto Correct system.

Like a lot of things in Office over the years, the new file formats have been instituted mainly to aid big corporations and organizations. For consumers and small businesses, the main benefit of the new formats is to shrink file sizes, but that benefit is likely to be far outweighed by the hassles and incompatibilities they introduce.

Luckily, you can set up Office 2007 to ignore the new formats and save your files in the old formats to be read without conversion software. But some new formatting features may not be usable in the old formats.

Free conversion software is available now at office.microsoft.com. Click on the Downloads tab and select Microsoft Office File Formats Compatibility Pack.

Mac Office users will have to wait until later in the year for Microsoft to release converters that will allow their version of Office to read the new file formats. But a third-party conversion program, for Word files only, has already been released. It’s called docXConverter, and can be downloaded at www.panergy-software.com for $20.

In another move that will likely annoy many consumers, Microsoft has stripped Outlook from the low-price home version of Office. This version, which costs $150 and can be used on up to three computers, was formerly called Student and Teacher edition, and now has been renamed Home and Student. Formerly, you were supposed to have either a student or a teacher in your household to buy it, though stores never checked this. Now, that pretense has been dropped.

But this edition of Office has been made less valuable for many folks. It still includes Word, Excel and PowerPoint, but now, instead of Outlook, it has OneNote, a very nice program for creating and organizing notes and other research materials. Many home users would prefer Outlook. But to get Outlook in Office 2007, you either have to buy Office Standard for $399, or buy a standalone version of Outlook for $109.

If you’d like to get more out of Office, especially in the area of how your documents look, Office 2007 is a big step forward, and worth the steep learning curve it imposes. If you’re happy with Office now, or you mostly create plain documents where formatting and design aren’t high priorities, it may not be worth the effort to buy and learn the new version.

Email me at mossberg@wsj.com.