I have to preface this post with the following fact: for my governmental contracting position, the laptop provisioned to me has Vista Business Ultimate. And it seems to work ok. There are some limitations, but there are enough work-arounds.
However, my consulting business has a machine that runs Vista Home on it. The machine's sole purpose is to run Quickbooks. I'm learning Quickbooks, which is no big deal; but the task is made infinitely harder by Vista. For almost every action I make in Quickbooks, I get a "Server Busy" message and I have to switch tasks. The machine runs Zone Alarm, and I'm constantly getting alerts that Windows Mail is trying to access the trusted zone. Huh? Windows Mail? I'm to the point where I just want to downgrade so that I can run the one application I need to run and get on with it. Because of these issues, I really don't recommend Vista to clients when they ask. I generally recommend XP when asked, or, if I feel they can handle it, Ubuntu.
It's just so mysterious because I'm having a (relatively) good experience (knock on wood) with the laptop provisioned for me for governmental contracting.
There, I feel a little better.