The epic quests are listed under each character-toon type page on this website. They start at level 7 and finish at level 50, but in total are about 10-12 quests. If you don't do one, you can't do the next step. Each quest gives you a jewel, weapon or other item plus exp and gold as well, so I think it's worth it.
The mother load is the Epic armor you get when finishing the final quest at level 50. But this armor in today's game isn't nearly as good as PC level 51 gear, when adding in spellcrafting and alchemy procs. I was told by an oldtimer that the Epic armor used to be the top of the line stuff, but that was years ago. Even though you couldn't pay me to use the Epic armor (since I have a Legendary Armoror and Spellcrafter), it looks cool as crap and the quests are a fun diversion in the game if your bored. Most the quests I've done can be done solo except for the level 50 ones, although this may be different with different toons.
So I say do the quests for fun, but get your armor from a player, SC it and proc it.
Edited, Wed Mar 2 11:42:27 2005 by stevenmeadows