My $0.02 :
I stopped using OD and WB when I moved to XP x64 a couple of years ago. The need for more memory, multiple core support, faster (64 bit) I/O was critical for my small business, and I've been running XP64 stably with no problems for over a year now. This is a 99.83% uptime system (less than 1 hour/month downtime), and when I trialled Vista x64 "Ultimate", it was "ultimately", hasta la Vista

.
For some users, Vista will be perfect. For most others, especially "high end" users (and please note, I'm not categorising anyone based on their use of the software - I consider myself a gamer AND a business user/developer), XP x64 is significantly more stable, if not as pretty to look at.
I regularly deal with 12+ gigabyte audio files, and 100+ gig video files, and Vista just couldn't be relied on to deal with large data movements. Period. (This is on a quadcore AMD board with 16G ECC RAM and 3.2Tb mass storage, with a plain old ATI X1600 with 64-bit drivers that mostly work well). I have a number of customers who tried to get Wifi working on Vista (32 and 64) and it's a nightmare, with bugger all support from the hardware developers (who are looking beyond Vista, since it's basically a new UI and some security layers glued on to an XP core - and I speak here with my MSCE hat on) AND from MS. (Google "wifi problems vista" and you'll see what I mean).
So Vista is no longer on my radar - I fought
that 800-pound gorilla for over 3 weeks until I had to give up in disgust and go back to XP64. (This was on a pretty tame hardware system as I've described - nothing bleeding-edge or beta on this box).
The sudden appeal of multiple core systems (when a quad core computer is advertised on Harvey Norman, you
know multicore is now mainstream) means that most multiple CPU users will probably get Vista bundled, so I can understand that's where the development budget is going to go to. But there's still a significant minority of us XP x64 users out here who can't (or won't) trust Vista for normal use. Most (but maybe not all) of us have supported or at least tried to troubleshoot x64 driver and hardware issues, and I don't see such a "self supporting" user base as being a significant support load. And as one of that minority, I'd definitely appreciate some cosmetic surgery support for XP x64.
NextStep and Workshelf are supported on XP64, it'd be great if we could do some app skinning as well...
So please consider some support for WindowBlinds on XP x64, even if it's only for the current release and no further, it would be a great bonus for users like us.