Dell Latitudes still have both the pointing stick & the glide pad. Mine also has a fingerprint reader built in to the glide pad.
Well, my Vista laptop (Latitude D830) will happily hot-undock. My previous XP laptop (D800) would get unstable & have to be rebooted. I don't know if it's the hardware or Vista but the new laptop is smarter about what it does when it transitions from AC to battery. For instance, if it detects no wired LAN connection it disables the hardware -- leaving wireless on -- to preserve battery.
Vista Ultimate includes Bitlocker so you can encrypt your hard drive w/out extra software. With IT Security my day job I consider drive encryption mandatory on laptops.
The only reason to run XP is if you have legacy peripherals that doesn't have Vista drivers.
Vista has a slightly different look & feel so you will have to get used to things. But the built-in search is way better & more integrated than XP ever offered. I don't even bother to drill in menus a lot of the time. Just hit Start & type in a partial file/program name. Start-"cmd"-Enter for a command/"DOS" prompt.
Vista on identical hardware will be a little slower but then you're not running it on identical hardware. Vista does more under the covers so naturally it needs a little more oomph.
UAC isn't the bother people make it out to be. It only really occurs when you do sysadmin or other non-user type activities. Personally, I think that's why reviews dissed it so much; they don't act like users & spend an inordinate amount of time futzing with settings that simply aren't touched during the process of actually using a machine. If you power up, browse, edit docs, etc. then you won't even see it. When you run things that aren't done often, like updating the users on the machine, it may prompt.
Vista is the present & future, XP is the past. And if you still want the garish green Start button on occasion you can always run XP in a VM.