Hi shumigirl,
We were there shortly after the Gringotts open two years ago ... did the whole HRH 5am wake-up/get in line/friendly walking sprint to the waiting area, get on then get on again via single rider etc. etc. etc.
We're going back in late August (weekend of the 20th) - wondering, how much have the Gringotts wait times subsided?
A bit of advice for Disney Diva, and for anyone else who hasn't been, Diagon Alley, especially at night, is, in a word, "Magical."
Love grabbing an ice-cream, walking around, and taking in the sites and feel with the family.
I'm not a 'huge' Potter fan, but there is next to nothing this amazing, themed, and immersive out there IMHO: WDW included ... & I love WDW.
If you do nothing else, please do yourself a favour and hang out in Diagon Alley when the sun goes down.
Have fun - Uni is great!