I ordered a set of Caruso steam curlers from folica.com.  The manufacturers and reviewers claimed that there is no damage.

Well, I got them and tried them, and the curlers are absolutely wonderful!  There is no heat -- they are barely warm when you roll them into the hair.  They work by dampening the hair, and the special foam roller design makes them and the hair dry quickly. 

After experimenting, I find that with the right size rollers and not too big of sections it performs extremly well, and the curls I did yesterday lasted long enough (though relaxed quite a bit) for a full, curled pony tail today.

I would definitely recommend it!  It's a wonderful invention.

There are many more reviews on folica.com -- the biggest complaint was about the durability of the unit.

I had caruso curlers given to me as a gift years ago, and I must say that I agree with you.  They are very gentle and easy on the hair, the only problem was that I never had the patience to put my whole head up in rollers and then wait for them to dry...I wanted instant results.  Patience is a true virtue, and I don't always have it!

Yes, I got some dents toward the root only, but mostly I positioned the covers at the bottom to not pinch the hair in.  I hope I can explain this clearly, but I only got a dent at the top roll, not every couple inches for every roll on the curler.

I guess it depends on how you will use them, but for my loose curls I can just smooth the small dents with water because where the dents are my hair lies flat.  But they weren't really bad at all.

I got the ionic, and I haven't experimented with not using the ionic option, so I don't know if the ionic is better.

Folica.com was nice, and they have a lot of interesting products.  I spent quite a lot of time browsing their website.