I’ve played a bit of the D&D next / 5e playtest. I tried the first packet that came out publicly and played it for three solid sessions, exploring much of the Caves of Chaos. From what I saw of it, I think it was a good start, but it’s still far away from being a real playable game. The balance, between characters and between PC’s and monsters, was far out of whack. That means that creating and choosing a challenge for players would be difficult.
I did consider playing D&D Next for my next campaign, even in playtest mode. I think conversion from the Pathfinder Beginner Box to D&D Next would be relatively simple in the future – especially if I keep only the basic races and classes, so I believe there is that option for the future.
I am hopeful for D&D Next. I’m intrigued by the modularity promised by the system, so a Basic/Beginner Box version should be easy to come by. I’ll keep my eyes open!