So I decided to spend a few points to unlock it now, expecting to have some fun in Spartan Ops with Jet Pack + AA Efficiency.
Nuh 'uh. The Jet Pack is garbage compared to how it was in Reach - You don’t get enough lift/energy drains too quickly. If you jumped and then used it in spurts, you could cover a good chunk of distance in Reach, which was especially handy on Caged.
In this game, it simply bleeds out so fast, and barely gives any lift that you are forced to use it all up in 1 go, because the moment you let go of the thrust you start to drop like sack of bricks - you simply can not generate enough thrust after letting go to counter gravity. This takes away a lot of the tactical advantages of the jet pack and I honestly don’t care for it.
Not only that, but the energy no longer recovers during use - Again in reach, the moment you let go it would start to recover, if only ever so slightly, which gave players a lot of mobility and options on certain maps. The jet pack energy in Halo 4 will not recharge at all until you touch ground. Imagine that this is because of the new AA Efficiency perk, which I can totally understand - you don’t want people flying indefinitely.
But the ability definitely requires some serious performance tweaking. I just don’t feel like it’s competitive at all, certainly not to the degree it was in Reach. No more shooting up like a rocket and raining down fire with the DMR 
Meanwhile, Active Camo is just straight up better than it was in Reach, which I love - so’s Hologram btw - so then why did this particular skill get hit so hard by the nerf bat?
EDIT: While I’m at it, Thruster Pack also feels horribly under powered. It’s saved me maybe a handful of times, and I do like the ability, but it’s not fast enough - the description is an absolute lie. I get that you wanted a new twist on the Evade ability, and as I said I think it’s a good concept - but the animation is simply far too slow.
If I’m quick enough on the draw, I can usually duck to the side to evade a grenade or similar threat, but as far as “closing the gap” goes to get in close - I’d say at least 90% of the time I’m better off just sprinting. Speed it up maybe 20~50% and I think it will see a lot more competitive use.