Roland has published a compatibility list for all its current relevant hardware, under the BOSS, Roland, and Edirol brands.
The table setup is a bit unusual. “Yes” means “will be compatible” in the future tense, but that apparently translates to “it works now”; links are included to 32-bit and 64-bit drivers. A dash means compatibility is unconfirmed one way or another, as you’re on your own with current drivers. A “No” means “We are sorry but we have no plan to realese the compatible software with Windows Vista.”
In other words, Roland/Edirol/BOSS have basically finished drivers for most of the devices they plan to support, and a lot of what isn’t supported now won’t be supported, ever.
Winners: USB, USB2 audio and MIDI hardware.
Losers: Older gear, bundled software, and editing apps.
Undetermined: FireWire (as of 1/31; I expect we’ll either learn it works or see an update).
The good news is, there’s a lot on the list: nearly all USB and USB2 audio and MIDI devices are supported, with only a handful of “legacy” devices excluded. The bad news is, FireWire devices are currently unconfirmed, and a surprising number of synths are on the “No” list. The original V-Synth (though not the newer XT) and Fantom-Xa and S (though not the X6, X7, and X8), and the SH-201, introduced less than a year ago, is being “evaluated” for compatibility with the internal editor, one of the major selling points of that synth. I’m assuming “incompatible” means the editor software is unsupported, though I’m unclear on why.
Overall, I’d say the Roland/Edirol compatibility picture is pretty good, and with dozens of devices on here, it’s certainly not fair to say “there are no drivers yet for Vista.” This is far more compatibility than the Mac had when the first Intel Macs appeared. But, that said, watch closely for what isn’t compatible before you get stung — there are some popular devices on the incompatible or unconfirmed list.
I’ll try to get more information, but otherwise, you should consult the Roland page for the latest information rather than CDM; only major announcements will appear here since Roland has it covered.