Garth mentioned that he was running Vista 64 on his laptop. I've been running it on my Latitude D531 for the last month or so with few issues. I had some initial touchpad driver issues, but I found a driver for the 630 that would work on Vista x64. Cisco doesn't have a full VPN client, but the AnyConnect SSL VPN client works well.
On the bright side, it performs well compared to Vista32. I haven't run XP64 to see if it performs better or worse though. I have the RAM maxed out at 4GB, so it's nice to get the full compliment when running VMWare Workstation on it.