Though I'm currently running two epic-level campagins (the characters are 25th level in one and 21st in the other), I've always favored low level campaigns. Characters have to contend with a ton of factors, and I enjoy being able to throw an orc with a greataxe at my players and have them worry about what will happen if they get hit. Critical hits are spectacular at these levels as well, and magic isn't outrageous. Now, this isn't to say that epic level campaigns don't have their appeal as well (as I said earlier, I'm running two of them!), but I just don't have enough experience with them yet to be good with them.