Cstfx summed it up pretty well. The only thing I would add is that for begginers a dealing desk FCM is probably better. With ECN's, at least the Interactive Brokers FX ECN, it is a lot more complicated to compute margin requirements, pip cost, and overall position value in base currency. I am a consistant profitable trader and I have used FXCM for over two years now with no issues. I have heard many other traders recommend Oanda and GFT also. Good luck
Yes and No. Yes it's an ECN and all money in your account is swept into their universal account which has SIPC protection (do a search on RefcoFx) plus you can hedge the futures against the cash and vice versa all from the same account. No, it's order management system is not as fluid as other brokers and margins tend to be screwy: in a dollar based account, if you trade the GBP/JPY you are margined on both the GBP and the JPY whereas with other brokers, the margin is based on only one side of the trade. You can trade any size, but they have 2 "exchanges" to trade: IdealPro, where most of your 25k+ trades would be executed with fairly tight spreads, and Ideal, which is for smaller denominations which tend to have higher spreads. Plus if there is a problem, you have to deal with IB's notorious customer service. You have your trade offs by using them.
Borkers + credit cards, think of it this way: having a broker that takes credit cards for depositis is akin to casino floors with cc cash machines available to make it "easier" to access your money.