The physics makes sense. larger rotors are more efficient because they have lower disk loading. At really low loadings you can lift a human with their own power.

The sikorski prize was claimed a few months ago.

http://www.youtube.com/watch?v=syJq10EQkog

you can get a 600 or 700 class that can do "3D" flying as in the video for much less than 5k. The entry point is below $1k.

their configuration makes sense to get the best features of both. it's not solving all problems but it's an improvement over quads for some tasks.