Also, quick question: Do you know how Mythic Adventures might play with E6? My guess is not well, and I haven't had an opportunity to try it out in my regular games yet, but I really like the concept, and think it could be worked really well into my campaign.
Also, where can I find a good source for E6 rules? I did try Google, but nothing definitive leapt out at me.
I added Mythic abilities to my E6 game, but in a limited way. Basically, as a reward for completing a "mythic challenge" (ie., the aforementioned dragon), the characters received 3 mythic abilities that I felt were appropriate to their character's concept and playstyle, with a very limitied mythic pool. I tweaked some of the abilities downward (mostly reducing duration, especially from an always-on ability/option to a limited number of times per day--I think all required a mythic point to activate).
This gave characters some interesting rewards that could occasionally yield exciting gameplay moments without altering the feel of the game dramatically.
I also had E6 capstone feats that essentially bring characters up to level 8 in terms of class features.
We also used some of Kolokotroni's magic item replacement rules (he's a RL friend).
Overall, most of the players really enjoyed the game, and it maintained the feel that I prefer: heroes aren't THAT far ahead of everyone in the world, and have to be scared still of some lowish-level threats, rather than transitioning to god-like status.
The only reason the game ended is everyone was so busy it became impossible to schedule anything, and I got frustrated trying to pin down dates.