Shadowhawk-2D has been interesting for me (after playing Hunchback-4SP almost 100% of the time), having played it starting a month and a half ago: SHADOW HAWK SHD-2D 115 76 39 1.95 149 68 2.19 73,603 167,040 12:15:16
I'm leveraging the ballistic cooldown quirk to use an AC20 with SRM4's, so that their cooldowns are nearly aligned. This makes it interesting when fighting at short-range against enemies who have weapons with 4+ second cooldowns, because
sometimes I can squeeze two shots in before their weapons finish cycling for their own second shot.
Now that I've got 100+ games in it, I think the mech is OK. Certainly not a top performer, light on ammunition (which I compensated for by taking both magazine nodes and both missile rack nodes)... but it's good enough to have fun with in QP. It does seem to catch alot of hits to the CT, despite my use of instantaneously-firing weapons. They recently gave it additional arm structure quirks, but it could probably have used extra CT structure instead.
The HBK-4SP, by contrast, takes less hits to the CT despite me using Medium Lasers and dealing with the extra face-time for the burn.
The AC20/SRM slow velocity also makes it hard to hit lights and more nimble mediums, and even heavies can be difficult to hit at the edge of optimal range. In games where I find myself shooting mostly at lights and mediums, or shooting at near optimal range, I get very little damage done. It is more effective shooting at bigger targets up closer, but that's danger close trying to trade punches with heavies and assaults. It acts as a good wingman for another "manly" assault, since you can corner with him or JJ over his shoulder to add to his firepower.
The arms actually are decent shields (as opposed to, say, the Hunchback-4SP's skinny arms), so although it does catch a lot of CT hits if you're trying to actively engage, if you're just fully shielding 100% of the time, the arms are perfect for that. Just make sure to turn your legs aside so people can't shoot you in the crotch.