Although we still don't have a direct answer on the power levels of characters in the 4th edition relative to previous editions, I think that with the information that has become available since we started asking this question, we can now safely say that a character of a given level will be less powerful than a character of an equal level in the 3.X edition. This is because it seems the various landmark abilities and spells that WotC considers problematic have been removed from the game and others have been shifted to higher levels. Note, please that I am stating this in a neutral manner, merely as an answer to a long outstanding question of power level in the new edition.