5 out of 5 rating for Age of Worms Adventure Path
Ran a Pathfinder conversion with a few adjustments from DMs who'd run it before. It's epic, classic, and has one of the best introduction dungeons ever made. You've got a save-the-world scenario with an ultimate bad guy, lots of lethality, great mysteries, and a lot of unique monsters. The only downside? It's going to take a long time to finish, and if you're moving to 5th, a long time to convert without help.