Green Armadillo hit DCUO's level cap (30) on Wednesday.
One thing that struck me about the experience was how much of the content I used on the way to the top. Solo missions are automatically granted when you reach the appropriate level, and I have completed most of them. There is one level 23 quest instance I skipped due to a massively over-tuned final fight, and two level 29 questlines that I have advanced to the final story instances but not yet completed. There may be some sidequests that I have missed - I don't know if the ones I have yet to complete are for level 30 or earlier ones that I missed - and there is also exp to be had for completing race courses in the world. That said, there will be almost no new leveling content for future Hero alts, and the Villain content generally mirrors the Hero questlines.