Render4you now supports NVIDIA iray gpu rendering.

GPU rendering iray vs. CPU rendering iray
Setup:
3D Studio Max 2014, resolution: 2400x1700px, 5000 iterations

Rendertime:

Single core I7 3770K: 15h:32m:31s, price: 7,48 €
Dual core Xeon 2650: 6h:27m:21s, price: 7,75 €
Dual Tesla K20x: 2h:38m:55s, price: 11,52 €

The dual GPU rendering system is 5.9 times faster than single CPU system with an I7 3770K and 2.5 faster
than the dual Xeon 2650 system.