[varispeed]

That should really be recorded in stereo and at least 20 samples for each key, possibly at different strength and then some sort of algo that would pick samples depending on how vigorously someone types.

Then that still wouldn't capture the intermodulation etc.

It's a lot of work to actually make it sound remotely realistic.

[tiborsaas]

+1 on all these, and don't forget that the keys make a sound too while they travel back to their resting position.