I've actually been trying to will myself to level my HBK mastery pack mechs...but god, every time I look at the limitations on the GI, I just can't bring myself to play it.
Rookie! I did all my mechs no quirks The only mech I have mastered since works came out is the Firestarter.
I haven't actually mastered any IS mech since quirks except the FS9-A heh...part of the problem is that I love my main mechs too much. My Ember/Jenner F are still my best mechs, and my 3L is my most consistently damaging mech. I've been loving HBRs nonstop, and avoiding my MLX/IFR like the plague. It's just hard to move away from my successful mechs in order to relearn a new one. That, and I just don't think the HBK quirks are anywhere near as neat as, say, Thunderbolt or Wolverine (I really want that 4 LPL Wolverine...)