Before Modern Warfare 2, I played World at War, and then the original Modern Warfare. I've avoided the series since then because its never since appealed to me - although FUTURE CODZ came close.
I'm tempted by this game however mainly because I just want a decent shooter to play through. The go-to criticism here is the failure to innovate, but then that won't bother a person like me who hasn't touched the series in so long. I think the dog gameplay looks boring, the space combat looks fun (and telling of a franchise desperate to top itself), and I'm a sucker for good customization.
How bad is the linearity in the campaign compared to the original Modern Warfare or World at War? (which I oddly enough remember better than MW2). How much better are the graphics and effects? Is there a Spec-Ops mode or a level replay menu, or a solid alternative? What advice (seriously) would you give somebody in my position, and what would you say is worth noting about the game that my questions don't cover?