If anybody gives you crap about sitting in an exit/bulkhead row because they want an empty seat next to them, just ask to see their seat assignment on their boarding pass. A little nastiness deserves some in return...
The preboarding thing is out of hand (see numerous other discussions). Along with the fact that FAR more than 1/3 of the remaining seats are handed out as A passes means that, just like college nowadays, almost nobody gets a C.
I thought the numbering system was more fair than the current setup. At least you knew there would be at most 30 people in the first group. Now it seems like 50 or so A passes is typical.
I actually love the B seat in the exit row. Along with the massive legroom, you get a larger carryon space than seat C and more shoulder room than seat A. If F isn't available, I shoot for B.