I use a Sandisk Extreme Pro 8GB card, with a rated speed of 45 MB/s. Improved the write delays a lot. I believe that it is important to format the card in the camera (which I always do anyway).
So I shoot jpeg and occasionally hit the raw button to get a particularly challenging shot in both formats. But the jpegs almost always come out better than anything I can do with the raws and have enough latitude for whatever PP I choose to do. The only camera I shoot jpeg with once raw support is available.