I've had my rear sway off for a couple of months now with no noticeable difference (Then again, I can't tell a difference between my stock shocks - one of which had lost its oil and was completely bad - and my new Bilsteins that I put on this weekend... so I guess I'm just not sensitive to vehicle subtleties).

Okay - to the question:
I assume that I'll need to put the bar back on when I tow something heavy... Usually I tow things that weigh 1000lbs or less - a small sailboat and a utility trailer... So at what point - if ever - do I need to use the sway bar when towing? 2000lbs? 3000lbs?