I'm hoping that either..
a. they give a choice of around 10 games rather than just one ot two so it doesn't mean that us people that have already paid for the game/s they offer miss out...again(like with the free Catan offer recently).
b. it's a brand new title so everyone gets the chance to download it for free, it's a bit unfair when the people that actively support XBLA by purchasing the games are the people that miss out when they offer up an already released title as a freebie.
Either way I think it will be a 400 rather than an 800 point game so I wouldn't get too excited just yet, even that's better than nothing of course though so I won't be complaining(as long as I haven't already purchased it

).
Would have preferred a point credit, that way if it is only 400 points I could put it toward an 800 point game and pay the extra should I choose to, haven't liked any of the 400 point games so far with exception to Jetpac & Geometry Wars.