Thanks for the feedback. My main concern isn't that they won't like the leveling type of advancement. I have already spoken with my players and they seem to like the idea. I was unclear on the execution. Right now I am thinking of awarding experience as per the norm in Heroes, but rather than giving it to them every session, experience will be awarded at the end of an arc during downtime. Then as far as spending the experience, I will consult them on how they think their characters advanced and offer new abilities for their level (to be purchased with the xp's). I was asking for input on how much experience would constitute a level. For example I was considering a large jump...like 25pts.
Another issue is magic equipment. Should I only allow it to be purchased with experience or should it be found through out quests. In fantasy games one of my favorite things to do is discover loot, but I don't really know how this will affect a Hero game. I have only played supers in this system.