First of all, IE8 was a pretty fine browser, aside from the performance issues. It introduced no more bugs than new versions of other major browsers introduce (and yet I don't hear anyone complaining about those).
Secondly, they're going to dramatically upgrade their javascript engine AND they're going to implement some CSS3 goodness. If they roll in svg or canvas, that's the holy trinity of what us web developers want from IE.
Granted, IE has a sordid history, but ever since microsoft restarted development on it, they've been noticeably improving the experience developing for it with every browser release, and IE9 seems to be set to do exactly that. So I definitely won't be complaining about IE9.
Well, ok, if they don't implement canvas or SVG, then I'll complain, but other than that ...
Yes, but unlike the rolling progression of other browser upgrades where FF users will upgrade, we will STILL have people running IE6. Maybe even 5 years from now! That's what galls me. The mindless, unbending sheep-like following that McSoft has now among corporate drone types. And the general drag this puts on development, and costs.
All our customers I know of that are still on IE6 are in the middle of a migration to IE7 or IE8. Once they're on IE7, I expect future upgrades to go much more smoothly.
Everywhere I see IE6 causing problems (Like one I just worked around where file uploads send the full path name with embedded single backslashes), they just say "can't upgrade, company policy", and just forget about the whole thing.