I really rather enjoyed the Batmobile sections and never found myself tiring of it... I even completed all the Batmobile-centric side quests.
I mean, I kinda understand people's complaints with the tank parts not fitting Batman's MO, but then again I say, why wouldn't he have various attachments? Non-lethal rounds make sense and even the 60mm cannon I could see for blasting through walls and such... I didn't find it quite as far-fetched as others. Besides, look at the Batmobile for TDKR, it had guns and no one complained.
Overall I thought it was a fantastic game, though I think I still prefer Asylum to the rest.