The 9 speed drive train that is currently on there is getting pretty tired. I've already stated that I wanted to swap back in the original XT crank set, (which I barely used, by the way), and a new chain and cassette, of course, would have to be put on as well. That also would include the green anodized Chris King bottom bracket I've had laying around for ever too.
I swapped in a Brooks saddle, a C-17, which so far has been great in combination with the titanium Regulator seat post. So, that bit is relatively recent in terms of upgrades. I could see going with a high end WTB Volt saddle at some point though. The combination of 'give' that the Brooks has in conjunction with the seat post is really nice, so maybe not.
My biggest beef as of now is with the brakes. I've fiddled and tweaked on the brakes for this bike for years. I think it is high time for a hybrid cable/hydraulic set up on here. I may just be getting something along those lines to solve my braking issues. I could migrate over my fully hydraulic set up on the Raleigh, but the length of the lines is maybe not right and well......that's messing with a good set up. I just do not wish to get that bike screwed up by taking off what works so well over there.
Anyway, the biggest upgrade, and one I have been talking about as well, is the wheels. I think I need to go to a carbon rim with some really nice quick release hubs and build a set this Winter for this bike. That would go a long way toward making these Extraterrestrial tires worth the extra weight. So that would, obviously, be really expensive. So, while that would likely make far more difference than anything else on the table here, it may be the most difficult to pull off due to the expense.
I can also see going for a carbon handle bar here also. If I did, it would be like the Whiskey bar I have on the pink MCD or a carbon Cowchipper, unless I can find something in carbon closer to the Luxy Bar. Like that would ever happen!