Has anyone heard the QSC K10s or 12s?
Yes. I mix a live band on the K10s every week at my church and I think they work very well. Their power response and dispersion is very consistent from top to bottom. They would probably sound a little rough in a near-field home music system, but they weren't designed for that. They have no problem filling a 100'x50'x50' auditorium.
I was at the NASCAR race last week and a local rock station was using K12's in the "fan zone" to blast their broadcast. Sounded horrible in that context but consider the source.