My wife bought an Isotherm last year and now we are trying to find someone to buy it off of us. Its main problem is that this semi-dry ends up being more of a full flood wetsuit then her old wet suit was. Here was her problem, because there is no exhaust valve, any trapped air in the suit tryst to escape when you jump into the water. She tried doing the scrunch yourself up into a little ball thing to get the air out, but she could never get it all. So as soon as she jumped into the water, the air was blown out of the neck seal. The neck seal was then really hard to tuck back in, especially with a hood on. She also would get a lot of flooding in and out of the arm seals if she would lift her arm early in a dive, the air would rush right out (and water in).
Her suit fit pretty well, but unless it was custom fit perfectly to you (i.e. no bunching areas that you cant get the air out of before the dive) prepare to be colder then in a good 7mm wetsuit. Or do what we are doing, save your money and just get a dry suit.