Slower than the fast HCs like the US Open.
It turns out that a ball travels slower post-bounce on grass than almost any other surface, including clay. However, the traditionally low bounce gives you less time before the 2nd bounce (i.e. the ball skids.)
With a higher bounce like today's Wimbledon grass, it definitely give the surface more clay-like characteristics, rather than HC-esque. The ball still falls into Federer's wheelhouse, thus enabling him his full shot arsenal from the BH side. But none of the shots have a lot of pace. For Nadal, whose ideal contact point is waist high, the slower-than-clay speed enables him to hit the ball more out in front, thus opening up the angles (esp. his inside-out shot.)