We installed an extra-high vanity, and I thought it'd be smart to raise the rough-in height accordingly. I don't remember the basic height, but I added the 7" or whatever the difference was.
Big mistake. I just got around to installing a temporary countertop and the basins Sunday, and there was a short period of panic trying to figure out how to make water run uphill (we also chose extra-deep basins). Eventually turned out very nice and we don't have a lot of pipe cluttering up the under-sink storage, but this experience has taught me that lower is better. They make tailpiece extenders, but not tailpiece shrinkers .