DHCP is working fine for me on a TiBook running 10.1. I'm running over AirPort.
When I first installed, I re-inited the OS X partition rather than installing over 10.0.4, and DHCP didn't appear to work. The problem turned out to be that I hadn't re-established the AirPort network. Once I selected my home network and entered the password, everything worked fine.
DHCP works with my quicksilver. And I upgraded w/out choosing to format. Try asigning an ip address that say your buddy has (and ask him to disconnect while you try this) manually to your osx.1 box, and configure any routing/dns... see if that works. If it doesn't, there may be something fundamentally wrong with 10.1, not necesseraly in dhcp.
BTW, /sbin/ifconfig -a will show all network interfaces.