Ya, I think her Portal success went to her head. Very very stupid to leave Valve at such an early time in her career. The sheer amount of knowledge contained in that building... people spend decades trying to get into that company and she was handed it on a silver platter after her and her team came up with a good idea.
I occasionally wonder if Swift will crawl back to Valve when Airtight inevitably closes (the company's output has gone from retail game -> PS360 and PC DD game -> iOS exclusive).
Is there any way to add custom soundtracks to Tony Hawk's?
Not to my knowledge, but you could just play your own stuff externally.