I've always stayed in an Essential Place. Anything more than that is not needed in HK imo. You're only in the room for sleeping.

Prices tend to start at around £140 if I remember.
It sure is, and as some previously pointed out the MTR is a very fast, clean, and cheap subway system. The train is usually a nice break from the heat too as the carriages feel like a giant wind tunnel. Make sure you download the MTR app. The MTR map can be invaluable for a first time visiter. It'll be second nature to you within a few days though.
Some quick highlights for me from my first visit.
Harbour City, in TST, was the best mall I visited. It is catered for pretty much any budget compared to some of the one's in Central.
A trip to the giant Buddha. Going from Central to Tung Chung on the orange line then a fun ride on the Ngong Ping cable car.
The Aviary in Hong Kong Park, Central.
Great wine and pasta at La Piola.
http://www.terra.com.hk/
Thai food at Ayuthaiya. Part of the Aqua group but not priced like it.
Aqua Tokyo/Roma/Spirit. For an expensive, but fun night out.
http://aqua.com.hk
Sky100 for a great view on a clear night.
http://www.sky100.com.hk/en/
Victoria Peak. If you're adventurous you can walk up or down it rather than getting the tram.
Museum Admission is free on a wednesday, and most are well worth the visit if you're into that kind of thing. The Heritage Museum was probably my favourite. On my visit they had a huge Pixar exhibition. It's a little out of the way but can be reached by 2 MTR journeys and a quick 5 minute walk.
http://www.heritagemuseum.gov.hk/eng/attractions/attractions.aspx
Awfully Chocolate for the best Ice Cream, ever! There is one located in the Langham Place Mall opposite the hotel.
The Star Ferry. If you're not in a rush to get from Kowloon to HK Island. I suggest this route at least once. It is my go to choice for crossing the harbour most of the time. It is even cheaper than the MTR.

For a great source of info.
http://www.hongkongextras.com/
I think my favourite memory has to be the Cheung Chau bun festival in 2011. It was such a hot sunny day but a great experience.
I could go on and on, but I'd be typing all day.