It's been a while since I've been to Disneyland - almost 10 years! The last time I went was to the one in California, and I guess every different disneyland you go to has a different experience.
As a matter of personal opinion - I found it much more enjoyable to spend two half days inside Hong Kong Disneyland instead of pushing for one whole day and getting tired with the queues and waiting. Random information people don't tell you: The Minnie Mouse hairband cost me HK$108 (about S$19.00). Don't bother getting the fast pass for Space Mountain or Buzz Lightyear Astro Blasters - their operations have been perfected to a T so there's hardly any lining up. What you should miss is the Dumbo ride (you know where it flies up and down). Way too slow and not enough capacity. It's also only a little more expensive to get a two day pass to Disneyland (HK$499 instead of HK$399), oh, and above all, you MUST catch the fireworks show at 8:00pm every night - I literally got goosebumps when the sky lit up over Cinderella's Castle!

It's amazing how tight a hold our childhood has on us, years after we've long grown out of our adolescence. I think I appreciate Disneyland more as an adult, maybe because I understand the value that it brings - more than just experiencing disney, but being a kid again.