I've been using a variant method of leveling based on game sessions for the Lost Continent campaign and have been very happy with it. I found it over at Swords Against the Outer Dark. It is not foolproof, for sure, but it works pretty well, and fits perfectly into my "low stress" methodology. I've house-ruled several mechanics in my campaign so far--clerical spells, magic point system, thieving skills, and several classes and races--but most have been directed toward hip-checking the game mechanics out of the way so we can play the story/game better. My players and I love to see a cool story develop. So letting them be the type of character they want to be, while challenging their skills as players, is where I focus.
Thanks to Shane Mangus over at "Swords" for the great idea. (His blog has a ton of rad stuff, btw.)