I have been using IB forex for two years. I love it, sure it's got a learning curve compared to many of those one click order brokers. The spreads are great, and if you can get your volume, you commission rates improve. The 2.5% leverage is a bit high when compared to many other brokers. Profits are deposited in the base currency of the pair your trading, and you can just leave it in your account until it gets high enough and then you convert it. So you can even time your currency transfers.
I never have any idea what's going on in IB. It all seems to work out, and I don't have any problem with the fills, but I can't figure out what goes or what it all means. I just click and hope it works.