I was reading through this thread, and there were a lot of good responses, some for limping, but most for raising. So here's my take on this.
Obviously, the table dynamics dictate whether or not it should even be a possibility to do this. If it's at a table that is very loose and aggressive, and there's a fairly high expectation somebody is going to raise, then sprinkle a limp in, but as a general rule, that play should be the exception rather than the norm. As others have said, you run the risk of letting others get into the pot for cheap and your chances of being outflopped are so much higher. Remember, it's still JUST one pair.
Raising should be the play the vast majority of the time. You still want to try and narrow down the field to one or two opponents so that you maximize your potential for winning a big stack. Of course, the dream scenario is you have AA, and an opponent has KK and there's a good chance (s)he will be giving your their entire stack.
I'm not sure a shortstacked player, to touch upon one response ITT, should ever limp with Aces. Keep in mind that you're likely going to be called if you shove by somebody who has a pair or a big Ace. Plus, by limping, you are certainly telling the table that you have a big hand, because if you're only putting in 1bb of your remaining 8bb's, the appearance is that you are waiting for the other 7bb's to go in because chips are valuable.
A shortstack is NOT going to limp with suited connectors, or even a small pair hardly EVER!!! It's telegraphing your play.