What you need to take into account with Epic is that everything is lenghtened - research, construction, tile improvements.
However, two things are at the same speed as Normal. These are unit speeds and (AFAIK) revolt time. Also, it costs the same amount of money to upgrade units, but you have more turns in the game, hence using a few turns to get cash for upgrading your army will not set your tech back as much as it would under normal.
Epic is basically a good speed to wage single-era wars in.
edit: so if you don't wage wars, it might seem to take a lot longer.