I heard (from second and third-hand reports) that Nuon had no fp performance to speak of -- it was a Jaguar-like architecture, with everything (game logic, 3D T&L, and rasterization) done in microcode.
Think of it as a TransMeta approach to 3D - with similar lackluster results.
Graphically the some of the games looked like a cross between the PSX and the N64 in visual quality. Other games looked really rough, like bad Amiga ports.
The core idea - provide games "for free" on top of a cheap DVD player - wasn't bad. But the game console was very low powered, and hard to program, and just sort of got lost in the noise.
(I also think maybe it wasn't a cost-effective DVD player.)