I know several members of my family have been waiting to buy a new desktop because they wanted Vista. How do you go about copying all your data between the two machines and what if you want to use both until you get comfortable? No problem. First off, I've found the Easy Transfer Wizard is VERY easy and works really well. It just copies all your settings and files to your new Vista machine, no problem. Also if you are upgrading or installing on your old machine, either your settings and files will come along during the upgrade or if you do a new install you'll find your files in the Windows.old directory. That's one of the many benefits of .WIM, it's nondestructive.
So what if you want to bring home a new machine? You run the Easy Transfer Wizard and bring in all your wireless settings, files, Email, etc, but how do you go about using both machines until you're sure you have all your data and feel comfortable on the new computer? No problem. There's a great tool available for no cost to sync files between computers. It's called FolderShare and is available at FolderShare.com. It's one of the MANY Live services that I talk to customers about and it seems that only around 1 in 10 are aware of. If you aren't taking advantage of these tools you're really missing out!
FolderShare puts a slim client on your machine and is managed mostly using the web. I use it to sync our family photos to an external hard drive at one of the grandparent's homes and I sync their photos back to my Media Center. It also is great for sync'ing home and work machines, two home machines, or in this case an XP machine and a Vista machine. I'm running it on my 64-bit Vista machine and it works great. In fact, you don't even have to worry about reconfiguring your home firewall or router because it operates as a client. Your machine makes a request to the server to determine whether it needs to sync and then the server hands off your connection to the other client. The server doesn't actually store anything, because both clients are making requests they take advantage of the same rules in your firewall that let you out when you surf the web. Of course if you have two machines sitting next to each other you don't likely have to think about firewall issues except the local firewall in XP and Vista which get "unblocked" the first time you run the client.
Finally, because Vista has pointers in the file system for application compatibility that refer to old folder names in XP, even the links to places like "My Documents" in FolderShare go to the Documents folder in Vista. If you want to sync to the Pictures or Music folders keep in mind it is no longer under "Documents" in Vista. It is now in the root of your profile under your username.
I find this tool to be really useful and leverage it in many creative ways including sync'ing the desktop on my Tablet back to the desktop on my home office workstation.