I use the Wet2Straight ones and find they are great. My hair holds the straightness amazingly well, even after washing it, which means it doesn't need straightening so much all the time. Not good if you only want straight hair occasionally, but brilliant if you want straight hair regularly.
I don't use them on dripping wet hair. I towel dry my hair a fair bit and leave it to dry naturally for a while with leave-in conditioner. Then I use some heat protecting spray before I straighten. I try and only straighten two or three times a week - my hair looks fine for the first two days and stays perfectly straight, and if it's not clean enough and I don't have time or can't be bothered to straighten it, I just wear it up.
These straighteners will work on wet or dry hair, and I have only had good experiences with them. Obviously you have to be careful not to straighten your hair too much, (every day is just stupid) and use something to protect it from the heat. But I had my hair cut two weeks ago for the first time since April and my hairdresser said I had hardly damaged my hair at all. Only really the ends, which she cut off anyway.
Just make sure you use a good-quality pair of straighteners, and only use them on wet hair if they are specifically designed for that. Also use deep conditioning treatments. You don't have to spend a lot of money. Superdrug do a really good coconut oil one - a big tub for £1.99. Sometimes if I have a weekend where I'm doing absolutely nothing, I'll rub some olive oil into my hair on the Friday night. It takes a few washes to get the grease out, but looks fine by Monday, and it really puts the moisture back into your hair. Also make sure you get a good hair cut every few months.