Several kinds of nerdery combined: I play D&D online via IRC, using a script for dice rolls. We play 3.5 ed; I have no experience with 4th. Sadly, our group is somewhat too large -- we've got like a dozen people, which means that we've got around ten or so players in any given session. Combat always takes a long time in D&D, but when you've got more than twice as many people as the system was designed for, it gets a thousand times worse...
That said, it's great fun for the most part. Right now one of the campaigns we're running is Planescape -- a damned entertaining setting. Party is currently being stalked by the quori, a nigh-invincible race of monsters created by nightmares (which I believe were originally from the Ebberon setting). Given that damn near no one knows of their existence, and reality on the Outer Planes is shaped entirely by belief, our master plan at this point is to create a sitcom starring an adventuring party on the Prime Material and casting the quori as Team Rocket. If everyone who sees the show believes the quori are bumbling idiots, they'll eventually become bumbling idiots. Sadly, the airwaves in Sigil (the capital city of the multiverse, as much as such a thing is possible) are currently controlled by the Anarchists, a faction devoted to the destruction of the other dozen or so factions. So we have to find them (which is a feat in and of itself, given that EVERYONE is ALWAYS trying to find them, they're very good at hiding), steal their teleprojector (the device that lets them broadcast), and barter it back to the Sensates (another faction, who are the ones who are supposed to be in charge of the airwaves) in exchange for airtime to show our anti-quori sitcom.
Yeah, Planescape is awesome.