I've been using it for years. Never a problem. Many nice features, except the limited 10 day intraday data.
ITs quite good, however you need TWS runnign simultaneously as well. Sometimes this makes my computer crash, but its not technicaly QT problem but TWSs'. Its also quite cheap so its the best solution i've found for the money i spend.
IB offers a gateway access now, there is no need to run TWS itself. I did not try it, but have a look at this thread: http://www.elitetrader.com/vb/showthread.php?threadid=193564
Concerning cost/benefit I'm using QT for charting and Zerolinetrader for execution. It's a very nice and reliable combo!