I've played in 2 campaigns that lasted into Epic levels so far, and DM'd one.
The actual base mechanics and concet behind the Epic rules is fine and has no problems, it's just that the actual feats and magic items and such are very bring and uninspired.
When I was awaiting the Epic Level Handbook, me and my DM were both imagining it containing wondrous abilities, allowing us to take our D&D campaign (which was already in it's high teens at that pint) even further, and into the realm of Dragonball Z and such, innate energy rays, Fighters learning to fly and strike terror into enemies with a glance... truly fantastic things.
Instead we got a book full of "Even bigger EPIC pluses to hit and damage" and "EPIC flaming sword that does 4d6 instead of 1d6!" and "EPIC feats that give +1 to Strength!"
And don't even get me on the subject of the City of Union. A city in the outer planes, full of 25th level Commoners and 30th level town guards... just because! It was such an inane and stupid section (and it was nearly a 5th of the goddamn book!) that I seriously wanted to hit someone with my copy of the ELHB.
We were severly disappointed. Players Handbook II was far more inspiring for high kevek characters.
Since then, some more support and a few much more interesting feats on the Epic Insights column have helped a bit. Too bad WotC chose to abandon that article. It was the sole source of further Epic lvel rules info, and te ditched it. Way to go, WotC.