Theron said:
Yeah, because it's the players' god-given right, NAY
obligation to try to break the DM's precious story at every turn, and cry foul if they can't.
Kinda. I wouldn't say they have an obligation to break the story. I'd also say that the players shouldn't be willfully disruptive. Still, if a story is happenning to them, regardless of what they do, then it's probably a foul. It's called "railroading" and I refuse to play with a GM who does it with any regularity.
As far as the battlemat goes, I prefer using one. I don't differentiate between "complex" and "simple" battles most of the time because 1) appearances can be deceiving, and 2) players have a tendancy to try out new/cool tricks in battles they perceive as being easy enough and that can quickly change the complexity of the encounter.
Why do I prefer to use a battlemat? Because I remember that every GM I've played with and every group of players I've GMed for, there has been at least one time that someone just didn't quite "get" what was being related. Even playing with good enough friends that I was often able to finish their sentences I've had "what the heck are you smoking?" moments. Not out of maliciousness, not out of cheating, not out of rules-lawyering (although I've also seen all of those), but just plain miscommunication. Just because everyone at the table is human.
Since using battlemats, I've seen those moments almost vanish. Sure, there are rules disagreements, but nothing that involves "what do you mean I'm cut off?" or "There's no way I'd have been standing that close to the BBEG," or the like.
Are battlemats required? Nope. Do they make life easier? For every group I've played with, I could absolutely see an advantage. Do referrences in the books to "squares" rather than "feet" bug me? Makes me want to slap someone, hard, with my Players Handbook everytime I read one -- getting rid of referrences to "inches" one on of the best changes between 1E and 2E, let's not go backwards.