I am still very new to this but I did leave my first batch in the primary for exactly 4 weeks. I then bottled and let sit to condition for another 3 weeks. I was VERY happy with the results. I hope my next batch turns out as well as the first.
The ale I racked today was brewed on 12/16/08. That's just about 2 days under three weeks, and it's early for me! I like to leave them about 3-4 weeks usually, and then either rack to secondary or keg or bottle, depending on what kind of beer it is.
I think the risk of autolysis is way overstated. I've made about 250 batches or so, and I've never experienced it or heard of anyone having it firsthand.