I've been to HKDL twice now, and loved it both times! The first trip was part of our honeymoon and we stayed onsite for 4 nights. For me, it was a good amount of time to really take it all in, spend a decent amount of time relaxing at the hotel, do our favourites a few times, and greet some characters. The second time was only for 2 nights, and for me it was way too rushed and I felt like I was just scratching the surface of what there was to offer (but it was really only to check out Grizzly Gulch so it served its purpose

). Both times we went were quiet times of year and mid-week. Most rides were only a 15 minute wait max, and we got decent seats at the shows without having to line up for ages. Having said that, a lot of people say that a day is plenty of time to experience HKDL, and if you're used to WDW, you might find it difficult to fill in time. There is only one small park with only a few major attractions, and no shopping/dining district. There is a lake/recreation area which I haven't managed to find time to check out yet.
As always, there are pros and cons to staying onsite. HKDL is quite a hike from the main hub of Hong Kong, and there really aren't any other restaurants or shopping in the area. A lot of people do a split-stay (stay a few nights in the city, then a couple more at HKDL), which seems to work well. I have found HKDL a great opportunity to stay at a deluxe level hotel for the price of a moderate. The HKDL Hotel is just beautiful. We've also stayed at the Hollywood Hotel, which was nice as well, but if money was no option we'd always go with HKDL Hotel

Both hotels are an easy walk from the park though a nicely landscaped (and Disney-fied) path, or there's a free shuttle bus.
As far as other attractions, the only things that are on my must-do list are the cable car up to Ngong Ping, and the tram up to Victoria Peak. But check out PIO's TR to get more of an idea about what's around.
My TRs are both very detailed about HKDL, but not so much info about the rest of HK. Feel free to have a browse
