Like Drew, my stabilizer was blown when I bought mine (at only 30k miles, btw). I replaced it with a Roadmaster Reflex (coilover type) and it helped, but I have no way of knowing how much of that help was due to the old one being shot, vs the return to center spring. Either way, it did help a little with highway manners, but putting in a new OEM may have been the same.
My alignment is just under 5 degrees caster, the best they could do without replacing parts. It handles well, and I probably won't do any further modifications other than shocks soon (I'm sure they are shot too, but not visibly leaking).
Tire pressure definitely makes a difference. Don't use the sidewall pressure, with the ease of finding CAT weight stations, there's really no excuse to not know your axle weights these days. Once you have your axle weights, look up the tire pressure chart for your tires and set the pressures accordingly. It really does make a difference in ride/handling. I personally ended up using 65 psi front, 70 psi rear.