Well the portable and fast aspect is true, they are pretty small and use SSD's, so they are pretty fast.
But as I said, gaming will not be their strongpoint. I suspect you will get decent performance from one (~HD3000 integrated graphics level).
EDIT: For better gaming performance, look at the ones that have HD4000 integrated, or even better a dedicated GPU. You can see which ones have what under the Chief River selection.http://en.wikipedia.org/wiki/Ultrabook