Lots of people have problems with GMG. They seem to have cleared up the fraud problems, and the GMG Steam games being removed from a couple of peoples' libraries at CAG seem to have been isolated incidents, but the GMG thread at Cheap Ass Gamer still reads like a support thread instead of a sales discussion. Someone here was also complaining that they bought something, never received a key, and support didn't give them a refund.
Is GMG's service any good? I don't rate their site to be honest, runs like a dog for me and it's horrible to navigate.
Ive still got 59 quid of 100 left in my steam wallet, but I wasnt expecting to be buying a load of gear off other places, but GMG has been a lot better for bargains in its daily deals.
Bit reluctant to buy from them because of it.
I still use them for AMAZING deals, but I expect the worst. I tried to buy something the other day, and all my (many) payment sources failed (an EGer kindly helped me out). Tried to buy Gods & Kings today, and the payment went through immediately. But a friend of mine couldn't get their payment through.