I completely agree with Dawn Wolf. Although I haven't used Armor Lock much in Matchmaking, I've used it quite a bit in Firefight, and when I didn't time it right, I'd sometimes get slaughtered by plasma grenades. But when I did get the timing just right, I was able to kick some Covenant ass.
And I loved the Jetpack. It's perfect for getting to higher places in a hurry. Well, until you decide to go too high and die from fall damage. lol