Universal Studios is just as popular in our family as WDW.
There are many good things to enjoy at both US and IOA.
Firstly you have a multi-storey car park a bonus of which helps to keep your car cool, which can be a relief in the Florida heat.
Both parks are right next door to one another so you can walk quickly from US to IOA or vice versa without having to leave Universal itself.
There is an excellent shopping and restuarant complex called CityWalk which is outside both the parks, but makes the whole experience a lot better.
There is also a Cinema there too.
As for the parks themselves, IOA is more for the thrill seekers with coasters like Hulk/Duelling Dragons but has several excellent water rides such as Jurassic Park, Ripsaw Falls and the brilliant Popeye's & Bluto's Bilge Rat Barges - prepare to get soaked - probably not best ridden if the weather is on the cool side
There is also in my opinion the best ride of all Spiderman, a not to be missed indoor 3-d adventure.
There is also Suess Landing which is great for the little one's.
Some of the attraction's here are a bit wild but as most of them are outdoors you can at least decide whether you fancy riding or not, especially with Hulk.
US - is based around the movies and the overall theming here is a bit better than at IOA.
You have Twister, Men In Black, Terminator 2, Jaws, Back To The Future , The Mummy, Jimmy Neutron etc
Kids are well catered for too with Barney, Woody Woodpecker's Nuthouse Coaster, ET and the Curious George playground with water attractions.
In addition you have Shrek 4D which along with Spiderman are (in my opinion) the 2 best rides in Orlando.
You are probably better off checking out the link below for full details:
http://www.universalorlando.com/
As far as queue's go Spiderman, Shrek, The Mummy are probably the most popular so best to get on these early.
SW is totally different to any of the other parks and generally does not attract the heavy crowds also.
Despite thrill rides such as Kraken and Journey To Atlantis, the park is generally a much more educational experience, with tours on Penguins, Dolphins, Manetee's etc
SW is not a park we would visit each year and 1 day would probably be enough to see everything. One other thing, maybe because of the vegitation etc but it always seems a couple of degrees hotter walking round here than anywhere else.
With that in mind we prefer to walk around SW in the evening, when it's quieter and cooler.
http://4adventure.com/seaworld/fla/default.aspx