I've used the booster to sidestep incinerator cannon blasts from close-to-mid range when I wouldn't have time to jump or sidestep normally. It's also quite helpful for dodging a surprise 'nade, at least for me. Not helpful for traveling faster, but think of it as a weaker version of Reach's "Dodge" ability. The better mobility it offers can be quite empowering when used right. :D
I like the idea of the thruster pack, it's almost like a 'luck button' in terms of getting in for a close kill or behind cover at the last second when shields are down. The problem I have is how slow it is, there seems to be no difference between thrusting and just walking.