I have Office XP Small Business Edition on my laptop. Rather than buying PowerPoint (at least for now), I downloaded OpenOffice and have done a little bit of messing around with its presentation software. I've also been playing around with the word processor. It takes some getting used to, but I think I could use it exclusively if I had to. There are some quirks that I hope get ironed out (and I suspect they will). I make a lot of outlines. The numbers or letters of the outline change formatting to conform to the first word that follows them in OpenOffice. If the first word following a Roman numeral is bold, the Roman numeral becomes bold as well. Little things like that will keep me from wiping Office XP from my system anytime soon (besides, why would I?), but if OpenOffice keeps improving, I may not put another version of Office on my future computers--especially if OpenOffice comes up with a replacement for Outlook (or if the Chandler project turns out a winner). I also put a version of it on my wife's desktop. She only has MS Works Suite that comes with Word XP. The thought of fairly complete office suites on both computers that didn't cost me anything is kind of appealing.
I've been using OpenOffice exclusively for somewhere around 2 years. It's easy to get rid of those annoying quirks -- go to "Tools" -> "Autocorrect/Autoformat" then mess with the options there. It usually takes care of all those weird quirks. The only thing I don't like about OpenOffice is that it takes a bit longer to start. Other than that, it's tremendously easy to use, it's featureful, works on OS X, Windows and Linux.