I'm in love with Jesus and proud of it!
I used to use it when I was a novice reach player because it was, to me, a novelty at the time. "You mean I can't die AND I can blow up vehicles?"
I quickly realized that AL is worthless. People just wait for you to come out, and when connections are bad it's an INCREDIBLY cheap and frustrating tactic. I'm sure I'm not the only one who's played on a bad connection where somebody goes into AL after being shotgun-melee'd.
AL beatdowns after a failed sword lunge or melee are the worst. Same applies to shedding stickies... it shouldn't be allowed, PERIOD. If you get stuck, you deserve to die.
I gave up AL about 2 months into playing Reach and swapped it out for Sprint and Camo (depending on the map and my mood). I began to play much better, and now I only use AL in Score Attack or when I'm in a vehicle happy BTB match.
In short, it makes the game a lot less fun. I exclusively play SWAT now, so I rarely have to deal with AL anymore.