Careful, Surface is now a brand of various computers, PixelSense was the old Surface Table with a display where pixels included cameras, but is now used to describe the new Surface's screen. So let's summarize:

* old Surface: a table.

* new Surface: a brand that started out with tablets but now includes a convertible laptop, a desktop, and a conference room computer.

* old PixelSense: a renamed old Surface with new fancy (very cool) display technology that includes optical sensing pixels, but seems defunct ATM.

* new PixelSense: the screen of a new Surface (high resolution, capacitive touch, stylus).

(disclaimer: used to work for Microsoft but with no inside knowledge)