I think the backpacks in Red Faction:Guerilla are a much better comparison to AA's in Reach than Shadowrun's Magic/Tech. RFG had pretty much identical backpacks to the AA's in Reach, Sprint/FleetFoot, Camo/Stealth, Jetpack, and Armor Lock/Heal is the most loose comparison.
I liked how the Jetpack and Fleetfoot worked in RFG much better than Sprint and the Jetpacks in Reach. Fleetfoot is more controllable and smoother than Sprint, and the thrust control in RFG is much better than Reach.
Comparing Reach's AA to Shadowrun's magic and tech is a disservice to SR, because you could combine abilities and switch them around at any time. They were also much more balanced and versatile. In Reach, you are much more constrained to a certain play style based on the AA you choose, you can't adapt as quickly and the Abilities in SR are more varied and lend themselves to improvisation.
I'm pretty optimistic for the full game, hopefully with some tweaks (nades, melee, spawns, weapon balancing) and some better maps I'll have a new Halo that I'll enjoy playing. Halo CE is the only Halo game I love and think is great, every other one is been pretty mediocre. Not bad games, just bad Halo games.