Optimal settings for Sleeping Dogs on the PC through Steam.  I purchased my copy from Steam and these settings make it VERY playable on a Macbook pro hd 4000 with 13 inch screen and a tiny i5 processor.

Best settings for Sleeping Dogs:

• Enable quality Anti-aliasing – normal.
• High res textures – on (download high res textures as a free DLC from steam).
• Shadow resolution high.
• Shadow filtering – off or low or normal.  I forget what the options are exactly for shadow filtering but the left option!  If you set it to the right option (high) then it works well in city environments, but when you get to the water it will drop to a 1 FPS slideshow.
• Screen space ambient occlusion – normal.
• Vsync on.
• Enable quality motion blur – off.  This is an optional preference setting.  I set it to off.
• World density – extreme.  I don’t know what this does exactly, but setting it to extreme had nearly no effect on the frames per second.
• FPS limiter – off.
• 3D depth – 0.
• 3D convergence – 10.

Bonus tip:

Remember to update the Intel HD 4000 graphics driver for Windows for a massive performance boost when using Bootcamp.  The standard intel drivers for Windows 7 loaded when installing Bootcamp are over 4 years old.