Same old argument, I've used Turntables, CDJ's and MM. It's an ever progressing field, you can do more with CDJ than TT's, you can do more with PC software than you can with CDJ's. All 3 mediums require skill, just different skills. I no longer use vinyl as I lost all mine in a house fire years ago and trying to replace 30yr old vinyl is near impossible.
Switched to CDJ (the early ones wern't that good it has to be said) but even if I hadn't lost my vinyl would still have made the switch, imho it's just a better piece of gear.
I now use MM to build sets, once you're competent with the program it takes no time at all to put together a standard set. When i talk about a standard set I mean laying down tracks to see what works. It makes building a set so much easier and quicker than spending hours behind the decks.
I have never used MM to play live, still using CDJ for that, but MM is perfect for making mashups, the ability to use 3 or 4 track overlays is fantastic. Call me a cheat I don't care, but the ability to make the mashup, save it as a track in it's own right and then use it in my live set to me makes perfect sense. Why would I want to risk ballsing up using 4 decks!
Anyway this vid says more than I ever could.
http://www.youtube.com/watch?v=vPjXZQBxzys It's all about the music.