I tried them a while back Tristan. £30 to review 3 songs as I recall. To be honest the critique wasn't anything special comprising about 1-2 A4 pages of very general comments. Nothing that you couldn't get on a forum like SOS for free !!!
Caragan does appear to have some respectable 'industry' people behind it and there is an argument that part of your fee buys access to their contacts (if THEY think the material is sufficiently meritous or not in my case).
You pays your money and you takes your choice.