I think the most difficult chisel to sharpen is the v-chisel. There are so many ways it can go wrong, since it really is like sharpening 3 chisels – 2 flat ones, and a small gouge at the corner. They all need to work together to create a smooth, clean edge.
I generally leave the edge flat across, but there are several professional carvers who grind all their v-chisels back – sometimes to a 45 degree angle where the v corner is set back farther than the edges. I have one v-chisel that is slightly set back like this, and it does glide through the wood nicely. I get more concerned with beginning woodcarvers re-grinding their chisels on a grinding wheel if they are not familiar with the technique. Things can go bad quickly. My advice if you are first starting out, is to leave the chisel as the factory grind, and just get it razor sharp. It WILL go through wood as long as you can get the edge sharp.