Biggest upgrades for me was getting the LightBicycle carbon rims with hope hubs and Thunder Burt in back and Racing Ralf in front. Changed out my cassette to a XTR with a 42t one up mod and a 34 tooth Absolute Black chainring with XX1 cranks. Also changed out my seat to a 35 dollar chinese carbon saddle, ritchey aluminum seat post, ritchey 70mm stem and EC90 625mm bars, and last but not least, got rid of my stock Elxer 1s which were complete garbage and installed the xt brakes with Ashima Airrotors.
Bike at stock weighed in at 28.5lbs, I'm now down to 21.8lbs. Totally different bike and climbs and descends like no other!!! I'm finally on the most difficult trails in my area riding without dismounting and time trialing myself on others.