If you buy the thing, just know there were two different keyboards these things used and they used different keycaps so if you just find some keycaps off ebay, your chance of sucess are 50/50; might as well just buy a fresh keyboard since it won't set you back substatially.
Also, while it'd seem the bulk of the units that were prone to this issue have already died by now, there is an ailment common to the T20, T21, T22 and T23 models called "Blink of Death" that happens to a small percentage of units due to a few components on the motherboard being low grade.
Also, be on the watch for a crack in the keyboard bezel just above palm rest area and immediate right of the right arrow key. With that said, never handle one of these models by the palmrest.
All of that said, in good condition they're nice systems and are fully supported with all necessary drivers available in Windows 98, 2000 and XP. The T20, T21 and T22 have Coppermine PIIIs (100mhz FSB, 256kb L2), 440BX chipset, 8mb S3 Savage IX8 graphics and a single USB port. T23s have Tualatin PIIIs (133mhz FSB, 512kb L2), 830MP chipset, 16mb S3 Savage IXC graphics and two USB ports.