We had a lovely 15 or so minute walk to Island of Adventure. We got there before rope drop and waited with the masses for park opening- and then bee-lined to Hagrid's (along with the masses). Some people ran- we did not. We got there when we got there, taking advantage of our resort early park admission- and got in line. We literally waited 90 solid minutes just to ride Hagrid's.
We hit up all the sights in and around Hogsmeade and Diagon Alley. It was fairly crowded so I was so happy to have the unlimited express pass. It is a MUST to be able to experience the best rides with the shortest lines, over and over again. Be aware- there will still be lines- but the express pass line is certainly shorter than the stand-by lines. On the other hand, the regular express pass is also good to have, but you only get to ride each ride once. Staying at particular resorts adds the express unlimited pass to your reservation automatically- certainly a great perk that I wish Disney would consider.
We grabbed a quick lunch and my daughter & husband went to rid Hulk and other rides that my queasy-self won't even consider. My last ride was the Minions ride- which is always cute and fun- but the line is fairly long and SLOW- so be aware of that, regardless of express pass.
I spent the rest of our time shopping at City Walk while they got their thrill ride on. It was a busy- yet short day- but we had plans to head to St. Petersburg- so we did our favorite things and headed out.
I wouldn't recommend a 1 day trip for your first visit to Universal, but if you are a repeater- and know what you like and don't- you can easily hit all your favorites using the express pass or unlimited pass and by getting there early. Be sure to purchase 2 Park-to-Park tickets so that you can enjoy the Hogwarts Express Train- as that is such a great experience and you can't ride it if you do not have park to park tickets. (yes- they check)