Really? I run it on a PowerBook G4, and while it's sluggish, it's not entirely "unsuable". If a 10-year-old single-core machine can handle OpenBSD, I'd be amazed by even the slightest performance issue on a quad-core, hyperthreaded, modern PC. What's additionally surprising is that this is the case on a Thinkpad, of all things; IIRC, the OpenBSD devs dogfood OpenBSD pretty heavily on Thinkpads due to their FOSS-friendliness.

Does your laptop have an Nvidia GPU, by chance? In my experience, those do tend to have very bad performance on OpenBSD. Intel and AMD/ATI GPUs should work better.

Also, it's worth mentioning that OpenBSD's kernel has a whole slew of debugging and error checking features compiled in by default; compiling a custom kernel without such features can be done, but the docs don't really recommend it, since it becomes excruciatingly difficult to troubleshoot any problems with it.