Originally Posted by steve_cay

+1 !

IMHO:
The non locking "always mushy" fork on the 8.2 is a deal breaker!
The mechanical disk brakes on the 8.3 leave much to be desired.

The 8.4 has hydraulic disk brakes, front suspension that can be locked/unlocked while riding with a small reach, upgraded gear-sets and wheels etc. for a reasonable price bump.

After that you are talking about (for a more substantial price bumps)
- Remote lockout (reaching is easy enough while riding on the 8.4).
- Upgraded accessories (gear-set, brakes, tires), to the already good ones on the 8.4.

If you have money to spare, and want the best bike, go for the 8.5/8.6. If you are value conscious and have reasonable expectations, the 8.4 is a good choice and won't disappoint.

Personally I chose the 8.4, and don't regret "what I am missing".