Disclaimer: I am not yet endorsing this version in any way.
Our group test played DnD Next this past Thursday. We had been playing some mish-mash of Swords and Wizardry and 4th Ed (don't ask, I still haven't figured out how it worked). Fortunately, the pre-gen characters with the play test fit our group almost exactly so there was very little adaptation needed to convert the current game over.
The biggest difference was the amount of abilities that were is some way magical that the various characters could do - most notably magical light sources. This is great considering we are running around on either the plane of shadow or some reasonable facsimile.
Since we only get about 2 hours of game play, most of the game was tied up in puzzle solving, both in game (interactively talking doors - 2 that were in different hallways, not visible to each other, but aware of each other's presence) and the puzzle of the new rules-set. So, we didn't get to have a combat, but seeing how the various classes function out of combat was just as, if not more, interesting considering out little functionality 4th Ed provided for out of combat activities.
It should be interesting to see how the next session goes, hopefully some swords will get swung and spells cast in an aggressive manner.