I would counter that all your questions can be applied equally as well to pitching "the right amount". I do agree that I would chose other options before I start playing with pitching rate, but it is certainly another factor that you can control as a brewer.
I think of pitching rate similar to how I think of IBU's - the calculators out there aren't going to give you exact predictions that can be verified by a lab. But if you are consistent in how you use them, then they can give you a good enough ballpark to be able to make adjustments within a given recipe on your own system.
Good points. But what about the varying opinions on how pitching rate influences ester production? Some say less yeast equals more esters, others say the opposite.
I guess my main point is that adjusting your pitching rate is just another factor you can use to dial in a recipe. I don't have an answer to the ester production question. For the one recipe I intentionally pitch at a lower rate (dunkelweizen), I've found that it tilts the ester/phenolic balance a little more toward the phenolic side. That's as much as I'm going to claim. Everyone else is free to experiment for themselves