So, I decided to follow my own advice and try a LAG play. Very readable raiser makes it $20 to go from early MP, and I decide to call with QJo--probably the first time I've called a raise with that hand in like 2 years...

Ok, sure enough, when the flop comes ATT, he checks, as does everyone else, so I fire out $80. Well, as predicted, the raiser folds (I think we were looking at very close to 100% on that one), BUT... EP check-raises for another $100. I obviously fold (he shows me a T, and since he was worried about another A, I figure he had JT-ish, something like that)
So, my first big lesson here, when considering plays like this, is to watch very carefully for chronic slowplayers. I think you have to have them identified and be a lot more cautious if they're in the hand. B&M, I think you can also work on some physical tells to see if they look like they have something. This was the first time I had played against this guy, so I don't yet.
A second lesson, which really doesn't follow from the play of this hand, but which I don't think is bad policy: If you're planning on making plays like this, I think it's probably a good idea to refrain completely from stabs at unraised pots. Very high credibility helps, and these raised pots are much more important than limp pots.
And a third lesson, probably the most important of all: While it's certainly important also to watch players' behavior on unraised pots (for example, to get the slowplayers pegged), it's absolutely critical (and, I am quite certain, enormously profitable) to watch the exact betting sequence every time there's a raise. If you really focus on the way these hands are played, it's not all that hard to get some pretty exact reads that you can use later.
I've already got several players down with smaller raises on weak-ish hands (KT-like), but I think one will find that the MAJORITY of players up to very high levels (since it seemed to be the case last night at 10/20 on Stars, too) are actually what I'm calling weak raisers. They just don't make any kind of consistent strong continuation bet. And from my observations up to now, most of the time a weak continuation bet (in the extreme case, a check) means a weak hand.
I don't advise making this conclusion too quickly, as there are also some with whom a check actually means the flop hit them really well. Similarly with smallish bets. But as soon as you see variations in flop betting after a raise, there are definitely some very profitable conclusions that can be drawn--despite my initial failure this time.
One final note: For the moment, when I have a read like this on a weak raiser, my plan is to play pretty much all of my "LP limpable" hands (in position) to this raiser. That's still only 23% of all hands, so I don't think I'm in too much trouble as to appearing like a chronic raise-caller. And, in actuality, if I do end up showing down some weird hands that happen to hit big in a raised pot, I think it should buy me more callers on my sets (despite the fact that I'm clearly NOT playing QJo or such because I think it's worth calling a raise with, but because I think the raiser happens to be a completely transparent muppet).