@Arcturus
Buy it digital! Show it off to your friends! MGS is definitely worth $20. I'd say it was worth $40 to me just to experience a next gen MGS game and it has me super hyped about Phantom Pain. Only game I want more that Phantom Pain is Uncharted 4.
I was initially slightly disappointed with how short the main story mission was, but mainly because it was so fun to play and I wanted more! Luckily there are an extra 6 side missions and on the road to 100% extra challenges include S ranking all of those on normal and beating all missions on hard (minus Jamis Vu since it was DLC). And then you have to unlock all challenges for a trophy which requires you to beat each mission a minimum of 4 times total by doing timed challenges and tagging enemies. Twice on normal and two times on hard. I think it took me around 12-15 hours to reach 100%.