As far as I know, they're SIMD, not VLIW. In VLIW, each ALU can be executing a different opcode. In SIMD, each ALU is executing the same opcode, but with a different operand.

The ATI cards were VLIW which gave them advantages in fixed pipeline, but as more and more programmatic shaders turned up ATI moved more towards CISC afaik.

GPUs are actually "single program, multiple data" (SPMD) machines, as far as programming is concerned. Internally, I believe they're implemented in a SIMD-like fashion, with extra hardware to handle the single program aspect within each lane.