I've been running them for about 9 months now. I like them but only have the stock shocks and springs to compare to. They settled about a half inch or so after the first month. I definitely had enough adjustment to have it slammed, but the roads around me aren't great. They have a lot of dips and bumps so I had to raise my car back up. I was getting some rubbing in the fronts (18x8 +45 235/45) rears were ok (18x9.5 +40 275/35) with no fender rolling. If I remember right, there are 16 damping adjustments and I had the front at 8 and the rear at 10. I first tried to adjust the damping, thinking that it was too soft. I changed the front to 12 and noticed a little difference, but not much and still had the rubbing. So, I raised the front about a half inch. I think the damping probably makes a difference, but only in small increments from one end of the scale to the other. If you're going low, you'll probably have to stiffen it up. On the bright side, if you wanted to go for a slightly lower than stock, you can adjust the perches pretty high and you might be able to use some of the softer settings on the coilovers. Luckily, adjusting the height is easy once you get the tire off.
Make sure you get an alignment afterward. I didn't and drove the car for about 6 months with the negative camber. I had worn the insides of the fronts pretty bad and had to replace them. I switched to a 245/40 in the front and got alignment done. Had a little more rubbing on hard bumps so I raised it another 1/4 inch and all is good. The larger tire made up for some of the stiffness/rattling on the old tires, too. It feels really stable at higher speeds and hard corners. I don't feel the body roll or dip when braking that I used to have.
I don't regret my purchase at all and did all the work myself. I got mine on ebay from this place
http://www.ebay.com/itm/TEIN-STREET...?fits=Model:Supra&vxp=mtr&hash=item4addf65925. They took a couple weeks to get at the time, because of the port strike in Long Beach last year. I got new KYB mounts from Rock Auto when I installed the coilovers. For me, it was well worth the $800 spent.