I once had a couple of old Thinkpad 701's, the one with the keyboard that splits and shifts so the close laptop is a few inches narrower than when its open. They had 50mhz 486DX5 I think, or maybe 75. I upgraded one to an AMD 133, seem to recall a debate about whether it made any difference because of the 486 being dx4. I certainly didnt notice any. Motherboard swap was interesting as I got an IBM video to take me through it, but the parts are so-o-o delicate compared to a desktop. Still, its quite fun to hunt down old parts, though unlike desktops they are model-specific very often. Big row with a dealer over a hd that wouldnt run in it.
The two 701's had different types of LCD, one was much crisper than the other but went on the blink and died. The other was I guess an old TFT type, really blurry - in 3d games you left a constant trail of pixels behind you. They handled Doom all right. No CD drive so I installed bigger things by sticking the hd into a desktop and copying across. I discovered some wheeze that meant it recognised one partition as a CD drive [hence WC1 installed and played]. Nice caddy on them designed so you could just pull it out, so hard drive swapping was fast and easy. In fact that was a better design feature than the keyboard, which seemed to keep giving me electric shocks.