I recently put the Specialized Hardrock Comp Disc 2006 bike through some major surgery.
These are the results of the recent surgery: Shimano 2008 Deore rear derailleur, 2008 Deore front derailleur and 2008 Deore Rapidfire Plus shifters. I also changed to a 2007 XT Hollowtech II 48T touring crankset and BB, XT Chain, and 2008 XT 9-speed Cassette. I took out the heavy stock Marzocchi MZ-3 shocks and replaced it with an OEM alloy rigid fork.
Also changed the Witch Ditch wheels (with the Schwalbe Marathon Cross 1.75 touring tires I put on it) to Mavic 719 rims, with Shimano M475 hubs and Alpine Triple-butted spokes and Panaracer T-serv Messenger 26x1.25 slicks.
So much lighter now, and the shifting is clean and robust.
Previously, the saddle was changed to Lookin Xsenium, and the disc brakes to Tektro Aquila, and the pedals changed to Shimano XT M770 spds.
I think after this round, the only stock stuff on the bike now is the frame, seatpost, headset, and handle bar. Haha!