There is a known bug with Android and PPTP VPN. Some have been able to make it work without encryption but that's pretty much useless. Cisco routers are especially problematic. There is apparently a bug with negotiating the encryption level, at least according to my conversation with Verizon support. Our network folks are investigating how to get out Cisco network to talk to my Xoom. So no, I can't get it to work yet at my workplace.
Cheers.