I've played this concept several times, with several variations of the rules. Here are a few observations:

1. Mega Attributes make a *huge* impact on "perceived power". I never really realized this until I played a game where we disallowed all Megas. When your characters can't dodge bullets from a standstill, sway hearts and minds by simply talking, or outsmart a bank of super-computers, you're suddenly a lot less "alien" to normal humans. Additionally, the relative power of powers themselves drops significantly, because you no longer have all of those bonus dice...