I've been running the Windows 7 release candidate since it was officially downloadable (and a previous beta before that). I've got it on an old Pentium 4 laptop from 2005, a mongrel homebuilt AMD dual core machine (64 bit W7 version on that one), and a $200 Acer netbook. Other than a flaky old USB to serial adapter that barely worked under XP, I have yet to find any hardware that has no W7 driver support. I haven't had an O/S crash yet on any of the three machines, and they all run substantially snappier than they did on their previous O/S (XP or Vista).
So far, the only apps that haven't worked are a 2004-vintage media organizing program (which didn't run well under Vista either), some even older games, last year's Symantec security s/w, and the freebie suite that came with a new Panasonic point and shoot I got last week. Those are mostly problematic only on the 64 bit version of W7. There are also some annoying error messages when I try to run automated backups from the 64 bit machine to Windows Home Server, but Microsoft announced that Home Server will be updated in the next month or two to resolve that one.
All the Adobe apps work just fine. I use DxO on the P4 laptop (W7 32 bit) and the AMD machine (W7 64 bit), and it runs fine on both. Seems faster than Vista did, but I didn't run any controlled tests.
If you think W7 will follow the standard pattern of new Microsoft O/S versions being buggy and unstable at first, I think you'll be proven wrong this time. W7 is indeed based on Vista, but the interface is quite a bit improved (offering some really nice features not seen anywhere else, Mac included), and the underlying guts have been optimized to require a lot less from the hardware. For crying out loud, I run Lightroom 2 on the Acer netbook with 1G of RAM. And that's a 24,000 photo catalog, with all the Aero bells and whistles on. Try that with Vista, or XP for that matter.
Feel free to "wait for Service Pack 1" if you must, but I already find XP very painful to use now, and I won't even bother with Vista. The W7 RC version is more stable than Vista with the latest service pack. And I'm certainly no Windows fanboy; I've got Linux running on some of those same machines, I tried OS X on all of them (Decided to keep it on the Acer, which is excellent), and I have some dedicated Macs to use as well. I like W7 more than any of the others, hands down.