I've had no probs with the drivers on my 5770.
For the comfort of staying with nvidia, the price to be paid is about 100W more power consumption per card (more noise), plus the loss of HDMI 1.4a, UVD3, and DP 1.2 support.
It looks like you are moving up in pricerange, if you can still wait the 6950/6970 should provide further performance in November (and provide additional price pressure on the 470).
I saw you mentioned HIS earlier, is that who made your 5770? It sounds like I should wait for the 6950/6970 to make it to the streets and decide after they're released.