A while back. I liked their service overall and thought it was more reliable than eSignal (used it concurrently, now I use ensign & sometimes QT) at a significantly lower price. It's web browser based and lacks some bells and whistles that some stand-alones have, but that in no way should affect a good trader. I use ensign now because with IB the cost basis is about the same as Alpha, with more options to boot, but if I were still trading on a platform that didn't support ensign, I'd probably still be using Alphatrade. They have a 7 day free trial so you should check it out.
I looked at esignal, schwab and went with alphatrade. After a year it seems great. Never been down. Liked it so much I bought the stock (OTC:BB). If managment decisions were as good as the product, the stock might actually go up.