I'll lane split, with a few simple rules. I won't pass a moving vehicle on the right, but a stopped one, no problem. I'll pass a moving vehicle on the left if the lane is wide enough that he would pass me if he were the one going faster. I won't pass just because I can -- there has to be some point.
Despite all the whining you hear from motorists about cyclists who won't share the road, it almost never happens that a motor vehicle will pull right to allow a faster cyclist to pass. I say "almost never" because I recently had it happen for the first time! I was riding through a park on a road with a 15 mph speed limit, and I came up on a bus labeled "driver training" that was doing exactly the speed limit. He saw me coming and pulled right to let me pass, glad to see they're training bus drivers that way! In 12 years of commuting I figure I've passed 10,000 slower vehicles and that was the first one to pull over.