Well, my boyfriend Chris and I, Sheri (both adults in our late 20's early 30's) just got back. We spent 6 days at Disney and 2.5 days at Universal and quite frankly, we were not happy with Universal at all.
Spiderman was awesome. And T2 (which is NOT for children). That was about it. The other things they had were ok but more thrill ride-y than we care for. And the thrill rides pale in comparison to ToT. Also on Back to the Future, if you look over, you can see all the other people in other cars riding and it really breaks the illusion.
We like the experience of being at Disneyworld. We like strolling through the WS, riding Spaceship Earth and the fairy tale type rides. We like sitting on Main Street having a snack and watching the wonder on little kids faces.
You don't get that at Universal. I noticed a few things at Universal that I REALLY did not like:
1. Employees in costume walking around on their lunch breaks with soda and food. Tacky and ruined the illusion.
2. VERY clueless and surly employees. We only had one nice experience with a young lady who tried to help us get an answer to a question but she had no support from her fellow employees and thus we didn't get an answer. Pleasant people were the minority here.
3.FILTHY counter service places. Every table we sat down at had guck all over it; several outdoor tables had bird droppings. No cleaning people seemed to care.
4. Lots of people smoking in crowded areas and employees walking by not saying a word. (Chris smokes and ALWAYS goes to designated areas...and even then he MOVES if a child wants to look at something close by).
5. MANY highly innapropriate peices of clothing being worn. I know this can happen anywhere, but I think Disney would pull the person aside and ask that they turn the shirts inside out (or put shirts on in the case of women wandering around in string bikinis).
The worst one was a 10 year old boy with his parents wearing a shirt for some sort of biker group with a half naked woman on it; or the 14 year old boy wearing a shirt that said " I like sl*ts " or the young college age guy who was wearing a shirt with the word "s**t" in its message. This upstanding and obviously charming individual was selected for an audience participation and thus got stand in front of a large crowd of people wearing this wonderful garment. No employees seemed to care.
6. Overcrowding. Not lines. Lines are to be expected everywhere and we honestly didn't have much problem with this. But things like Earthquake, Twister and Posiedons Fury that require walking through with a tour guide, we felt cramped. I missed most of Posiedons , which I had been really looking forward to, because they squeeze so many people in that its hard to enjoy it unless you are up front, and I was not about to block the view of children, as many adults were.
7. Bad street entertainment. The Ghostbusters thing was esp. bad. It just was horrid. And when the guy playing Beetlejuice used the word "fr*ggin" in his dialouge, we actually decided to get up and leave. Not a curse word, but not really something that was needed to be said. The other "show" was some guys in a van breakdancing. 'Nuff said.
8. Characters just not fun. We met a bunch of the characters, and the people handling them rushed everyone along, even when there was no one in line. We had a few run ins with some nasty character wranglers (as Chris calls them)
9. Horrible music pumped through the park. At Disney you can relax and the music fits the atmosphere. At universal we had to listen to some terrible rap top 40 blaring through the park.
10. Tacky stores. City walk just did nothing for us. We enjoyed our meal at Margaritaville but we found most of the shops to be tacky and not places we'd ever go into again. The Endangered species store was nice. But we went into Dapy and it was mostly centered around Playboy merchandise. Yuck.
I don't know. I can't imagine spending an entire vacation at Universal. We might go back once in a while and go on Spiderman which WAS very good and check out the Mummy which I REALLY hope is good because if they ruin ancient Egypt for me, I'll weep.
Really, we spent 1/2 a day in each park and then went to PI for our evenings at the Adventurers Club.
We are 99% sure we are going back in early December for a quick Disney fix. We'll be skipping Universal and probably won't go back to Universal unless we are going for 2 weeks of Disney and would have time to take one day.
So I guess Universal can take all the cheap shots they want at Disney - as Chris says, they just don't have that Disney Magic!
(Chill...I'm joking with you!) 
