I'm no fan of Vista, I assure you, but it's here and IT support will have to deal with it. I'm hoping that SP1 will address many of the issues that have come up in the year-plus since Vista was inflicted upon us. Fortunately I've not (so far) had to support Vista authenticating to SME Server. Most of my business clients are avoiding Vista and buying new PCs from Dell and HP with XP, or getting Vista and then paying me to remove that and install XP. Home users are taking Vista up as they buy new computers, but I've removed a few Vista installs from home computers also.
If you have enough RAM (2 gigs+) and a superfast multicore processor Vista runs reasonably well, and I'm getting used to the many small changes from XP. Some are clearly "make-work" ... why oh why do you now change the workgroup from the "System" control panel applet?