While the artwork and fluff is up to a fairly good standard, there were numerous typos and errors which made the book confusing at times (tier 3 abilities listed in tier 1, for example.)
Some of the inherent imbalances in non-mythic are unfortunately amplified here. A mythic feat for a +1 bonus to attack or a feat that grants an automatic natural 20 on your init roll? Non-mythic feat taxes get their mythic equivalents here instead of having them dropped or replaced. Though I can see the rationale as this is a supplement to the standard character progression. The books says clearly "Mythic is not epic."
The gap between full casters, pet casters and non-casters get broadened quite a bit. Though granted there are certainly some choice picks for martials.
All in all a good solid way to really flesh out the feeling of being a "hero" (or anti-hero) in a group of heroes :)