The charts are the best, nothing I've seen, and I have not seen them all, comes close. The feed is pretty bad and even when the servers are "working" you can hook up to the wrong one and get a lot of bad data. I've seen problems recently with intraday volume, if you get the wrong server you will see volumes on a 1 minute bar that are greater than the 5 minute bar!! Their daily data is not scrubbed but their intraday data is, so you will see bad highs and lows, maybe even opens and closes, on the daily data. Even their scrubbed intraday data probably will not give you the same opens and closes as a high end feed like Bloomberg.
You just have to decide if you can use them for what you are doing. I need the depth of intraday data they provide so I check it before using it for backtesting. I would not even consider using them for trading in realtime, too many hassles trying to stay connected and to the right server, especially since there isn't much of a way to know you are on a right server except if it has been working for you recently. For realtime I'm going with Esignal and keeping others in mind as well. If I ever get out of "cheap mode" I might try one of the high end feeds, probably would never regret it, that's usually the way it is.
Max