The Star Citizen MMO has been financed mainly by crowdfunding with developer Chris Roberts, who also developed the Wing Commander series and Freelancer, at the helm. Parts of the game are currently in Alpha testing (Hanger Module, Arema Commander, Star Marine) with Squadron 42 being the single player option.
The game sports an all-star cast and, if the mocap we're seeing here with Hamill translates across the board, the cast alone should sell the game. When you have Gillian Anderson, Gary Oldman, Andy Serkis, Mark Strong, Liam Cunningham, Ben Mendelsohn, and John Rhys Davies in one place, it's bound to get interesting.
As for Hamill, the game's released a full cutscene to give fans a look at both Hamill and some of the dialogue choices in the single-player story.
He's not playing Luke Skywalker, but it sure is nice to see an alternate world where Luke may have become a military leader instead of a Jedi. Mark Hamill's just born for vocal gravitas.