Heres my two bits on the TS:
I have used most of the freshwater machines out there and there are only two I would stake any long term use on:
Fisher 1280 and the Tiger Shark
The T-Shark is a tad heavy, and its not my first choice on dry land. But it was meant to be used in the water, after all, where it's own buoyancy offsets the weight. I cannot stand body or chest mounting as it really monkeys with the balance when you get into the water. I also find the underarm mount to be a bother, generally. I settled on the standard below-the-hand mount on the pole, which balances the weight perfectly.
Where there is iron present, it is a treat. It pops, clicks and shortbeeps over small iron, while letting large iron through. Last year I found a nice pocket knife because of this. If it DISC'd out all iron, including the large stuff, I would have missed that knife.
It has a raspy edge to the large iron though, once you get used to it. Between this and the clicking/popping response of small iron, it is a great iron discriminator.
I run my DISC on 2-3, most of the time, which gives me the described effects.
And don't worry about that ED180 vs. 120 crap. That's for yakking about on the forums. Out in the real world of water hunting, the stuff you want to find in the water 'aint down at the bottom of the phase range (180), so what matters if it goes down there?
You need to discern small iron, get used to large iron and pick up anything else from foil on up. The Tiger Shark does that.
The SENS on the TS will get you in trouble. Try not to mess with it, as it comes from the factory. If you do, move it in minute increments only. Then try it before you make more adjustments. I repeat, do not get happy handed with the SENS.
DO turn the threshold up a touch from factory. This makes all responses sharper. And turn the volume upnear max.