I read this in the Wiki:

"42,000 miles roundtrip business class within N. America (use for UA 3 class flights such as PS JFK-LAX/SFO, Air Canada business class, and other flights where a front cabin is sold as business rather than first)"

.. and am really intrigued and interested - I currently have 45,147 miles and using it for UA PS by far seems like the best choice. Has anyone had any success with this? How do you check UA PS award availability?