It's not something I've ever thought about it. For me I think the controller has enough buttons. Persoanlly I couldn't see what else they could utilise one or two new buttons for. Games are becoming more complex but if we keep adding buttons to accommodate for that then it would eventually get a bit daft. By sticking to a standard number of buttons we force game developers to simplify things or at least not make them overtly complicated.

Do you have a GOLD account? Before I got GOLD I sometimes came across demos that were only available to paying members. If you have GOLD make sure it hasn't expired. If it's not that then I really have no idea what it could be...

It's always worth downloading demos. What better example of "try-before-you-buy" than to play a snippet of a game so you can garner some opinions of it beforehand? (Plus it's free...) I work in a GAME shop and too often I see people paying upwards of £45 for a title on its release date only to trade it back in a few days later because they couldn't be bothered to check out a demo/rent a copy/read up on recommendations and instead adhere to advertising and clever marketing.