We exited thru City Walk as usual also, however it was VERY crowded...shoulder to shoulder, heal to toe people as far as you could see! I'm actually surprised nobody got hurt. I saw several groups of people walking on the 'side rails' of the moving walkways (which thankfully they were smart enough to turn off!)...all it would have taken was a small slip and they would have fallen to the roadway below.
If Universal made a mistake it was not keeping the parks open later. Had they kept USF open until 11:00 and IOA until midnight they could have greatly improved the crowd situation.
Anyway, the fireworks were great and well worth the delay in getting out.