I think, the most user-friendly one is MJ Studio ( http://d-lusion.com )... You don't have to switch between the multiple windows (like in Virtual Turntables), all is on you the tips of your fingers, so to say. The interface is moreover intuitive due to it graphically represents two tts and a mixer (the interface is very eye-pleasing)... You can record what you've mixed, you can even record having one soundcard (you'll hear one channel in both speakers with the accent on the left, while th other - on the right), you have an easy-to-use 3-band EQ, AutoBPM, skip and all the stuff you need. One of the greatest features is keyboard binding (you can control almost everything via keyboard), which gives you more freedom, cause now you can do one thing with the mouse and another - with the keyboard.