I have used used them for a year now, eminis and occasionally stocks. Executions are good, order types flexible, service pretty solid. Their standard 'Navigator' client tool is stripped down (no DOM etc) but depends on your trading style. You can use Ninja or something similar with them. Their data feed is not eSignal, but you get to view 100 symbols at a time , although backfill data is patchy.
Open Ecry offer more futures markets, also good executions and service, ok free data feed, good charting (even has constant volume bars if you use them) and good DOM -type order entry. worth checking out too. They will give you a quote for commissions based on your volume. Most of the decent firms are very competitive and prices are similar.