I'm not the parent commenter, but I personally run OpenBSD on a pretty wide variety of hardware, most recently (among laptops, that is) a PowerBook G4 and a Dell Latitude D830. Most things work out-of-the-box, but there are a few exceptions:
* Power management is nonexistent on PowerPC hardware, so I currently have to shut down my PowerBook between uses, since I can't put it in standby. This is annoying, but workable.
* Hibernation is buggy on the Latitude. Suspend works fine, though.
* Both the PowerBook and the Latitude required the use of fw_update to install nonfree firmware (for the Broadcom-based Airport wireless NIC and the Intel PRO Wireless 3495abg-or-whatever wireless NIC, respectively). Also slightly inconvenient, but - again - still workable.
* Some things don't really work on PowerPC, most notably Firewire. A slight bummer, but hopefully this will be resolved someday.
From what I understand, IBM/Lenovo ThinkPads are - just like they are with GNU/Linux - among the best laptops to use with OpenBSD; IIRC, a lot of the OpenBSD devs dogfood pretty heavily on them, so they get a bit more attention. I'd avoid anything with Nvidia graphics, whereas AMD/ATI or Intel graphics should be decent.
* Power management is nonexistent on PowerPC hardware, so I currently have to shut down my PowerBook between uses, since I can't put it in standby. This is annoying, but workable.
* Hibernation is buggy on the Latitude. Suspend works fine, though.
* Both the PowerBook and the Latitude required the use of fw_update to install nonfree firmware (for the Broadcom-based Airport wireless NIC and the Intel PRO Wireless 3495abg-or-whatever wireless NIC, respectively). Also slightly inconvenient, but - again - still workable.
* Some things don't really work on PowerPC, most notably Firewire. A slight bummer, but hopefully this will be resolved someday.
From what I understand, IBM/Lenovo ThinkPads are - just like they are with GNU/Linux - among the best laptops to use with OpenBSD; IIRC, a lot of the OpenBSD devs dogfood pretty heavily on them, so they get a bit more attention. I'd avoid anything with Nvidia graphics, whereas AMD/ATI or Intel graphics should be decent.