I actually have a long sleeve one I use almost exclusively for XC riding and love it. They wash well and I never have any issues with being cold, all I wear in any conditions is a set of bib shorts, compression top, shorts, t-shirt and gloves. I am generally a 'warm' person though.
The circulation benefits are fairly well documented I believe, could be worth a try - obviously don't try and squeeze yourself into a small though, haha. Skinz do a similar item which I'm sure the 'big boys' will carry.