The Langham is a great hotel, and Mong Kok is a fascinating place. Just keep an eye on your wallet though, as there a few pickpockets about. For a westerner though in general, the Hong Kong streets are much safer than any major cities in Europe and the US.
One of the main things that will strike you here, is that although the image you have in your mind of HK is skyscrapers and inner city streets.....most of it is lush green forests. Make sure you go check out the New Territories, the whole Tai Wai/Sha Tin/Ma On Shan valley is an interesting look at modern town planning.
Hop on a bus from Central to Stanley, via Aberdeen, so you take in the whole south coast of the island, then sit on a sandy beach and stroll through the markets.
Sai Kung is a nice little seaside resort, where all the fishing come in and sell their catches on the pier, while the locals push their pimped up dogs along the seafront in doggy pushchairs (don't ask).
Go walk Lamma Island, 20 minute ferry from the bustle of central to something that feels like a small Greek island, full of tight little streets, restaurants, tat shops....and a nice hour or so walk through hills to a different ferry home.
Explore Kowloon....too many people here never leave the island....I like just going for random walks, Kowloon City has dozens of cheap Thai restaurants. Hung Hom has the rather interesting sight of a full size cruise ship full of shops, parked in the middle of a high-rise housing estate.
You don't have to drop silly money to take in the view. Most people will reccommend Aqua for a drink with a view, but I prefer Eye Bar, above the iSquare mall, which has a better view, drinks are cheaper, and is less pretentious. Michelin star chinese food there as well.
Go play dim sum lottery. Ok, so you may end up with some fish heads, but it's cheap as chips, and they won't be offended if you don't eat them. Chicken feet aren't as bad as they sound.
Oh and more food for thought....
Apple Macbook Pro 2011 15" core i7 2.2 GHZ @ Apple Store UK = 1,849 GBP
Apple Macbook Pro 2011 15" core i7 2.2 GHZ @ Apple Store HK = 16788 HKD = 1,324 GBP