I had no problems with them , but, after the MF Global debacle, I got nervous about "futures-only brokers" and I decided to close out my account at the beginning of the year. I was using NinjaTrader for free, with the Zen-Fire feed, which is more expensive than another feed that they started promoting more recently. I was paying around $4.82 round trip for ES trading.
Actually, they still send me monthly statements via email, with all zeros even, even though I pulled the money out a long time ago. It is kind of strange to still be receiving statements.