I agree with Dormouse. I have 2010 now, and I'm pretty happy with it. In particular, Outlook seems more stable, although it's still dog-slow, and the ribbon (of which I'm generally a fan) does more harm than good.
I really, really hate OpenOffice. Its performance is slow, it seems inaccurate (as DaddyDave noted), and it really just doesn't feel comfortable to me.
On the other hand, the SoftMaker product is a strong contender, other than that businesses seem ignorant of it. It's an order of magnitude cheaper, and provides nearly comparable functionality (except for not having a mail/PIM app, nor a database -- yet). It's fairly comfortable to use, and performance is fantastic. And it's nearly perfectly compatible with MS documents. I've got this on my main desktop, on my PocketPC, on my Ubuntu netbook, and portable on a flashdrive.