I prefer being the DM rather than playing. I never took a character to twentieth level until playing D&D third edition. I played a human fighter. I previously blogged how this character died, Total Party Kill as a Player Character,
I remember when Dragon Magazine issue #5 came out. Bill Seligman wrote an article titled "Gandalf Was Only a Fifth Level Magic-User". As a DM, I run into difficulty handling high-level magic users. In OD&D, a fourteenth level Magic User can have a Limited Wish spell once a day. I find if you have intelligent and creative players, the campaign degenerates. The campaign turns into a Wish War or mimics the Twilight Zone episode, "It's a Good Life".