I was a huge fan of the previous Tomb Raider games, so I was interested in this from the start. When I saw it offered on GMG for £17.55 / $28 I couldn't resist.
As for physical distribution, it's completely irrelevant in this day and age. And regarding the lack of a demo, obviously that will put some people off but it's not a deal breaker for me - I can usually tell from the preview media whether I'm going to enjoy it and what price I'm willing to pay. I tend to only grab demos for indie games I'm not sure about.