Should I ever.....

[rwanger]

If you end up having set over set, it's not going to matter whether or not you raised preflop...you're still going to get all of their money. So, if you are just limping in, it shouldn't be with the intention of trying to sneak in a set over set.

The only situation I would say to go for it is if there were some guy who always bet in position when checked to, and you thought you could check call him the whole way with your AA. This of course assumes that he will bail if you raise preflop, and if the guy truly does bet every time, you run the risk of another player taking the same line with a better hand than yours that he got a free flop with.