I had also heard that Andy Cutler doesn't like infrared saunas through a post on Cure Zone. Just found the original link again:

Andy Cutler on Infrared Saunas

I have also been thinking about buying one of the cheap portable FIR saunas. My only concern is that it is made of synthetic materials. I would be interested in hearing any experiences people have with these saunas. I know for myself that sweating definitely helps, unfortunately in winter it is difficult to generate much sweat when exercising.