It's still not a discussion
iWork 09 does not even import simple Microsoft Office files properly, but even if it would, you can still not properly export to Microsoft Office format either. And that is a huge problem in a world where everybody else uses that format and where you need to provide your files in a compatible format that others must be able to use, too.
The real show stopper here is Numbers. It might be a nice mini spreadsheet for home users and basic tasks, but it gets nowhere near Excel - and Excel still is the most important, non replaceable flagship application of Microsoft Office. And Numbers 09 already fires warning messages when it imports a primitive four column Excel table with a simple SUM function in it - at least it did so here when I tried it.
Keynote, however, probably is the one killer app that iWork 09 offers. But since I'm not giving any presentations these days, I couldn't care less. If presentations are your bread and butter, then you should probably buy iWork in addition to MS Office just to have keynote.
Pages vs Word is a nonsense discussion for me. Neither one is really good at what they do. For hardcore word processing, Mellel is a much better choice than either Pagas or Word, and for creative writing, Scrivener, StoryMill and/or Montage blow the Apple and Microsoft "competition" out of the water.
However, at least on the PC and Windows, Microsoft Office cannot be substituted when you rely on office automation or when you have third party business software installed that embeds or otherwise integrates the MS Office functionality. This has always been the ultimate killer feature of Microsoft Office and the real reason for its huge success - you can use it like Lego bricks in your own software solutions.
If none of this is even remotely important for you, than iWork 09 is an acceptable choice, and the price is okay. But depending on where you buy it, you can also get the Home and Student edition of Office:Mac for the same price, and then you also get a pretty good all-in-one-eMail/news reader/calendar software - Entourage - with the package. And you will also get much better compatibility to the world's de facto standard with much better and longer support and lifetime than any Apple software solution will ever give you. You'd be updating to iWork 10 next year while Microsoft will still give you software updates in five years from now. Longevity has always been an integral part of Microsoft's business solutions.