I tried a couple times in high school. We would end up getting distracted and go on tangents about crap unrelated to the game, or else we'd get in arguments over how the game worked. No one could stay in character for more than two minutes, and I think we only ever made it through one complete dungeon. It was always a complete and utter failure.
Although it seemed like it would be fun, it never was. I eventually just said "fuck it," gave up, and committed to just playing computerized RPGs instead.