I slowplay AA about once in 100 times, and even then I normally get caught out!! I much prefer to just raise with it everytime.

There's two main reasons for this:

1) I rarely limp in, so raising doesn't give away the strength of my hand
2) The more hands you raise with the more pressure you are putting on your opponents, even if you are raising with good hands

A heads up or 3 handed situation would be very different to a full table however and I would be more inclined to slow play as the stakes increase and the number of opponents decreases.