Simple sim again, single lens, but shaped better this time.
Amazingly, I'm getting >20k muts a sec rendering old Suzanne:

This is just 5 minutes on an amd64 3000 (14 muts/pixel) [CLICK FOR LARGE]
I've got a nasty, nasty scene for tomorrow. It's a little glass I drink whisky from, with an exr map, and I'm going to put dispersion on the lens.
Heres a render with a normal camera of the whisky one:

[CLICK FOR LARGE]