The PowerPoint presentation had problems when run in Keynote for iCloud under Internet Explorer -- simple transitions and animations didn't work, and several slides were garbled. When I opened the PowerPoint in Keynote for iCloud in Firefox, I received the message, "Your browser isn't fully supported. For the best Keynote for iCloud experience, use a supported browser." (Odd that I didn't get a similar admonition about IE.) When I tried Chrome, the transitions and animations didn't work, either, and graphics were garbled. Finally, I cranked up Safari in OS X 10.7.5, tried again, and saw black screens and that the message, "Slide couldn't be displayed. Do you want to try again?"
In summary, based on these tests, iWork for iCloud is reasonably good at rendering Microsoft Word docs and Excel spreadsheets, but PowerPoint presentations are beyond its ken. Simple changes to simple docs carry through, albeit with significant round-trip formatting changes, but simple changes to some complex docs can have disastrous results.
Will iWork for iCloud work for you?There's no simple answer. Apple is a newcomer to the online office game, and it shows. The three iWork for iCloud apps feel like they were designed from the ground up to unify the concepts behind word processing, spreadsheets, and presentations. Their interfaces are remarkably similar, minimalist, and easy to follow. The design is at once elegant and accessible.
But Apple's file interface stinks. Of the three major browser-based office suites, Apple's is the worst for handling files. The only simple way to get a file into iWork for iCloud is to drag and drop it into a specific app's Web page. You can't sync a folder on a Mac or PC with iWork for iCloud, as you can Office Online and Google Drive. And if there's a way to set up folders from inside iWork for iCloud, I couldn't find it.
If you aren't overly concerned about Office compatibility and you only work with a few documents, iWork for iCloud is an excellent choice. Experienced Office users will have to unlearn a lot they "know" about documents, spreadsheets, and presentations, but the clean iWork interface really shows through.
Further, iWork is free for all computers bought during or after September 2013. That isn't just iWork for iCloud, mind you. The offer also extends to the downloadable iWork suite for OS X and iWork for iOS, both of which are available in the Apple App Store.
As iWork for iCloud is still officially in "beta," it's entirely possible that Apple will charge for personal or business use in the future. But as it stands right now, iWork for iCloud appears to be free for all. If only Apple would bake in some decent file handling.