I'd like for levels to be a little less gradated. For example, I'm not sure the difference between 1st and 2nd, or 8th and 9th should be as marked as it currently is. What we find in 3.x is a sort of "lurching" forward at certain levels.
If you still get "toys" at each level (which is a good thing) while slowing down the overall objective power level, it'll make advancement fun without challenging verisimilitude overmuch: "I'm better than I was yesterday, but not superhuman compared to yesterday." I think such a notion would really work in a system that has 30 levels. You know, the whole "thinner slices of the same loaf" approach. Of course, I hope that we _do_ see something new at the higher levels.
As far as rate of advancement goes, I don't have a problem with it being a little faster with the above caveats in place, and I suspect that this may be the case (though, like everyone else who is theorizing, I have little actual proof).