I've used it for a few years now, it was especially good when i worked on the South coast of Cornwall and I used to make long runs up to Scotland and back over a weekend, just seemed to give you the extra boost to do the distance when you would normally be well past the fatique mark.... and it is good in summer as just under a long Tshirt..... washes quickly and drys quick too...
And if you are stuck for fancy dress at a rally...pair of pants and a towel add a make shift eye mask and your a super hero..