Hi there, we just returned from the WORLD after two weeks in absolute HEAVEN on earth .... we included Universal as part of our stay because we were going to be there so long (13 days/12 nights), and let me tell you that you can do it "all" in 1 day (both parks) if it's low season (such as now - September) but if it's busy - you really need at least 2 days. They have a special running of buying the 2 days/2 parks (Universal/Islands of Adventure) and you get the 3rd day "free" which you have to use within a week of purchase. We did the two days, and never returned for the 3rd day as we got sick of paying $11 for "preferred" parking (vs. $8 for regular parking, or $9 I'm not sure ...).
About the park: It's great! I've once heard that Universal has the "technology" over Disney ... not sure if I'd say that - but Disney and Universal both equally have a lot to offer people I think!
About the "Studios" part: The ET ride is just amazing! So cute, so creative! The Men In Black is really awesome too! Of course, Back to the Future is great as well! Really cool!!. The terminator 3-d movie is cool too. Basically there is nothing that is "not" cool! Jaws is an excellent adventure as well! I'm sad that they've stopped the "Kong-frontation" but such is life .... TWISTER is pretty neat (not a ride), and I missed the Ghostbusters deal as it was outside this time and I had no desire to stand in the sweltering heat any longer than I had too!! We can't forget about the Nickolodean (sp?) studious that are there for live tapings and if you have older kids (i.e., maybe 10 or so or a bit older) they love that!
Then on the "Islands of Adventure" site, they have the HULK roller coaster ride which is awesome! I black out though on the first couple curves and windings and I'm really not sure that it's a great idea for me to be on that kind of ride ..... (happened both times I rode it). Then there's this bobbing up and down deal that I think is captain doom or something -- TOTALLY not worth the wait at all! It shoots you up - bounces you like once or twice - and then you are DONE! Don't bother with that! The Spiderman ride is absolutely incredible! Then there's this REALLY awesome water ride - can't remember the name, but there's also a Popeye and Olive Oil round boat water ride they are BOTH cool! And you get SOAKED! Then there's the Jurasic park ride - that's GREAT! Then theres some more roller coasters over there (I think 2 or 3 more) and they are great too!
Basically, if I had to say is it "worth" it .. I'd say "yes" - they really h ave a lot to offer in two areas, instead of being like - one park here, one park there, one park there ... you know like at Disney: MK, AK, MGM and Epcot .... you are at least pretty much located in only 2 - very close together adjoinging parks.
Hope that helps! Oh too I forgot - tickets are NOT cheap - like to the tune of $80 or $90 per person (I think kids are a bit cheaper) - and when you add that to your very expensive Disney park prices - you almost have to gasp!!!
ENJOY!