Yung Kee is probably the most famous restaurant in the Central district, primarily because of its size and location, but also because of the high quality of its food. This is pretty much the gold standard when it comes to Cantonese 'siu mei', and I can't think of anyone else off the top of my head which serves such an expensive variety of the stuff.
The food here is indeed good. The last time I was here (though I've been here many, many times over the years), we got a selection of some of the more common, popular items that people typically order here: we ordered the cha siu, which is really the most popular siu mei item to get here. It's on the sweeter side, but has a glaze that is really excellently done, such that the meat is slightly crispy on the outside, but pretty tender on the inside. Other good items include the roasted goose, which tastes great and also has a good skin flavor- however I think the skin could be made a little crispier. We also got the garoper fish head with tofu, which is a pretty good dish considering it wasn't we usually ordered, something that we just randomly tried. Overall, tasted pretty nice.
The biggest 'problem' with this place is the price. The food is good, but probably still not worth the prices they charge here. It's actually not really worth it to come here in my opinion unless you have someone you need to impress. Still, this is not really a good date restaurant either, since it's kind of super brightly lit, and is somewhat loud. Yung Kee is best suited for celebrations for larger parties, which means your bill, even if paid on a per person basis, will probably at LEAST be around $300 HKD, perhaps more if you order more than two or three dishes. I'd recommend just coming here once in a while, and not necessarily buying anything to go.