For those that have just had the tactile switch fail and want to replace it it can be found at Mouser Electronics for $0.60 each.
Tactile switch
The item you want is figure "C" 101-TF25R-EV (at least this is true for the three button key FOB head on my 2004 key). I used the 400 gf switch for my failed unlock button, but comparing the operating force to the stock switches I think 300 gf would be closer to correct.
BTW the description says it is a thru-hole part. This is incorrect it is surface mount as shown in the picture.
De-Soldering and soldering this piece is easy. Just use a soldering pencil (get one at radio shack cheap) rather than a soldering gun.