I heard this and installed OpenBSD on my thinkpad only to find out there is no support for nVidia. I suppose you need ATI or Intel video to get a working X.
Check wifi adapter support also (in general, not specifically on ThinkPads).
Everybody else supports nvidia chips by running a big blog of proprietary code in the kernel. That kind of defeats the purpose of openbsd, right?
That's it in a nutshell.
Debian doesn't support them with a big binary blob; by default, it supports nvidia chips with an open-source driver (nouveau), which works fine for most things other than 3d gaming. It just hasn't been ported to OpenBSD yet, though there is interest in doing so [1].