So, we've both come down to the same place! Don't know if it'll get any cheaper for waiting a while, but when you need it for work it doesn't make any sense to wait. I did find CS2 for something just over £500 about a year ago but decided to wait for CS3.
I was thinking more that if you'd got an old copy of InDesign CS or, I think, Photoshop CS, they can also be used for a different upgrade path. I have a copy of InDesign CS I've been using for quite a while - I swopped it for an iPod - the person who bought it had bought CS2 by another route. It's registered with Adobe and legal and I can use that. I'm downloading the CS3 apps for the 30 day trials one at a time because I haven't decided whether to upgrade to the same CS3 as you or just upgrade InDesign and use my old Photoshop.
I can imagine Adobe tightening up on anyone trying to buy CS3 by the back door by buying CS2 and upgrading. I'd be interested to know what you do and your impressions of what you get.