No direct experience with them, but I know they are one of the few "real" STP brokers out there. I know a group of guys in Colorado who trade with them and swear by their execution. it seems to be a fixed spread/STP model though, which I have never really heard of and dont fully understand.
I remember they're listed on forexpeacearmy.com but I can't remember their rating. I recall that the ratings though were not seriously bad. Odd coincidence, I found by browsing that some of the most rated ones are ones used by Global Futures. They have real live human beings there although apparently there is some sort of conflict of interest with introducing brokers. I ordered a book that talks about that but haven't received it yet.
Been on demo with these guys for the past couple of weeks. The spreads today didnt budge during nonfarm - anyone trading live can verify that those same spreads could be traded on today?
GFS has contacted me several times and given me the full pitch. I finally broke down and agreed to use their demo package. It looked OK and had decent graphics. But I don't need all the bells and whistles. Just a tight spread. And when I compared them to my current broker (IB), they just didn't measure up. And that's because while they don't charge a commission, they do add 1 pip to their liquidity provider's quote.
I've gotten use to TWS so like it. I haven't tried the forex specific functionality. I just place my orders like stock orders.