I've been to Universal, I've done two days of it. One day for each park. We did it seperately from Disney, during a week when we were staying offsite (we stayed offsite the first ... 10 days? 12 days? and then went to Disney, and then on a cruise). I did not like Universal Studios, the rides were not for me. They were mostly more intense rides, and they weren't really anything I was like OMG I REMEMBER THAT FROM WHEN I WAS LITTLE. The stuff there, my parents would have been like 'Oh yeah, I remember that movie... it was alright.'
Island of Adventure was awesome. There was a good mix of faster rides and slow rides, and it was a fun cartoony environment. I love love Pop-Eye & Bluto's Bilge-Rat Barges. It's the best raft ride I've been on. I mean Kali is alright, but it's shorter and you don't get as wet. I kind of hated Dudley Do-Right's Ripsaw Falls tho... that was just... ugh.
I can't say the parks were anything special that I felt I needed to go back for. I mean, I will go back for Harry Potter some day, but other than that... meh. I'm not a ride person. I like to go see shows, and Disney puts on a good show. They're top notch. They KNOW live entertainment.
Unfortunately, I feel no pull to go back to Disney anytime soon either. I think when I went when I was 12, it was big, it was new and it was my childhood. The last time I went, it was still big, but it wasn't new for me anymore. I got hot, tired, cranky, and annoyed at the prices of meals. It turned me off. I felt cheap. It was a bad feeling. Maybe it's because I was staying offsite, I don't know. Maybe that might have made a difference. But I think it's just my getting older. Anyhoo, long story short, I still love Disney. I love the movies. But I won't be going back for at least another 10 years.