I have to say that, aside from Sonar and some low-latency issues, I have had VERY good luck and adoption of Vista as my primary. My work laptop, a Lenove x61 tablet works great with it, and unline the tablet edition of xp, it doesn't feel like an afterthought-add-on. On my desktop, I have two partitions, one with XP, and one with Vista. for the longest time, I was using Vista exclusively, but I went to work on a larg-ish Sonar project and I just couldn't keep it happy, so I flipped over to the XP side where it's been fine.
But I definitely LIKE Vista better as an OS and from a productivity perspective. Lots of shortcuts to get to things, instant search, context irrelevent document and email finding, snappiness of the system, etc. If they can get a few more things ironed out at low latency (or I have some time to get back to my Vista partition and check if 7.0.2 is working now) and/or Echo gets their new WaveRT drivers to work right with Sonar in WDM mode (i.e. not ASIO), I'll be happy to make the switch.
I also own a tech support company providing support to small->medium sized businesses in the Atanta area and I don't yet recommend corporate adoption of Vista, even if for only the learning curve, expense, and the IE7 mandates that are issues for some of my clients and the web sites they use. But if someone is getting a new special purpose machine or is plopping one into a "standard" office machine, running typical apps like Outlook and word/Excel, Inet browsing, etc, I don't have issue with the move forward, as it's generally been pretty painless for me and my use and for a lot of other IT folks I know. Of course, a pre-built system is going to have all sorts of extra "fodder" on it, so it's likely to be a botched/bloated install, so that's possibly a different animal.
You certainly have to know a few things about your "stuff" to go into Vista to make sure it will all work, but especially for the "common user", Vista is pretty good, and for the power user, it has some great opportunities that just kill XP for me.
HTH