It'll be fine.
"Man of Steel" wasn't a great movie. 56% rotten and 55/100 on Metacritic tends to back that up. But what it did get VERY RIGHT were the action scenes. Superman moved and fought like you'd expect to see Superman fight. While the movie as a whole was kind of hacky (blame Zack Snyder), it was arguably the best depiction of a comicbook-come-to-life that I've ever seen (blame Zack Snyder). So...
#1 - Expect to see the most accurate depiction of Batman's fighting style to date. No more clunky, poorly choreographed close-up action shots. Batman will be agile. Batman will be athletic. Batman will kick serious ass. Whatever martial arts stuntman dons that costume is going to look amazing. You're going to love it.
#2 - As much as I loved 'The Dark Knight" series, Batman often took a back seat in those movies. He wasn't nearly as compelling as the villains. I'd go as far as to say that in TDK, Batman was downright boring. Heath Ledger entirely carried that film, imo. It's a fact. It's one of the reasons why I prefer "Batman Begins" to TDK. The Nolan Batman movies were great, but let's not overrate the Nolan-version Batman depiction. He was just aiight.
#3 - Christian Bale was a solid Bruce Wayne, but I have little doubt in Ben Affleck's ability to play Bruce Wayne. He absolutely looks the part. He absolutely has the range and intensity. He absolutely has the acting chops. He gets a bad rep for some misfires, but for the most part I've enjoyed his work. Some of his early work like Good Will Hunting, Boiler Room and Dogma were money.
http://www.youtube.com/watch?v=UqDtf1aw818 http://www.youtube.com/watch?v=CSQYRq8kf4gHe was perfectly fine in recent films he directed like "The Town" and "Argo".
Are you really trying to tell me that this Oscar winning filmmaker isn't good enough for Zack Snyder's hacky cash-grab rushed visual-driven sequel to his "Man of Steel" live-action cartoon? Come on. This crap will be fine. It certainly will not be on the level of Nolan's work... none of Snyder's work is. In fact, this silly half-assed movie will probably get critically panned even harder than "Man of Steel". Snyder has yet to make a critically acclaimed film. This will not be any different... But at the end of the day, you're going to enjoy the heck out of seeing Ben Affleck's Batman do his thing with Superman. It will be comic panels come to life, man. The action scenes will be worth the price of admission. Relax.