Did the mod last night, swapped the TMG600 for a Lite-on 163D (i think).
The biggest problem i faced was getting the thing to fit correctly in the space that was left by the old-xbox drive.. had to 'modify' (nice word for hacksawing) the bay a bit, and also the Lite-on's tray to fit the xbox-front. But, now that it's all done it works a treat, games boot lightning fast.. The noise level went up since this is a pretty fast drive with (very) high RPM's.
Well worth the effort..