Mind you, most of my experience is from the rails 3 days plus some legacy application support.
My biggest gripe is the autoloader; it makes finding where something comes from extremely confusing when ramping up new developers on large, mature projects.
The enforced, common convention is a boon and a curse- consistency across projects is an obvious benefit, though I prefer a different structure myself.
Beyond that my gripes are more related to ruby and the tooling rather than strictly with rails itself. Of course you can tweak and configure rails to behave any number of ways, but the more you do that the more you lose out on the primary benefit, which is the community one-true-way mindset.
My biggest gripe is the autoloader; it makes finding where something comes from extremely confusing when ramping up new developers on large, mature projects.
The enforced, common convention is a boon and a curse- consistency across projects is an obvious benefit, though I prefer a different structure myself.
Beyond that my gripes are more related to ruby and the tooling rather than strictly with rails itself. Of course you can tweak and configure rails to behave any number of ways, but the more you do that the more you lose out on the primary benefit, which is the community one-true-way mindset.