I have the 2012 rockhopper expert and have fiddled with a few bits.
Upgraded the forks to a set of reba team
Upgraded the wheels to superstar on crests gone tubeless
Chain, cassette and front mech to xt and taken off the big ring and replaced it with a 36 (If my memory is correct)so now running as a double.
Feels like a pretty competent bike now, have ridden massive natural terrain in the lakes (underbiked but it survived) to black and red trail centre runs and even a handful of xc and endurance races.
Forks made a huge difference, think it dropped 1kg off the weight and as someone that likes mile munching the wheels are a big help as well.