While the size discrepancy struck me funny, I never doubted Cruise could fill the role; I just thought Reacher as played by Cruise would be similar to other loner heroes he's played.
My comment on Jeff's post concludes:
In the best scenario for moviegoers, Reacher becomes so associated with Tom that they can't imagine another actor playing him. I'm not sure it would be best for Reacher to become one of many loner heroes Tom Cruise has played. I liken it to Jason Statham's playing Richard Stark's master thief, Parker. If you weren't a Parker fan already, you might easily forget Statham's Parker among the many tough guys he's played.
The more we see actors, the better we get to know their nuances. Over time, we pick up on every one, and later performances are more the character becoming the actor than the actor becoming the character.