Not quite a gimick. Alkan disapproved of enharmonic spellings, so modulations could wind up in some very unusual keys, like Fx Major. Feinberg uses a triple flat for much the same reason.
I quite agree... it depends on whether one is thinking in terms of reading the music more or less easily, or in terms of clearly showing the underlying harmonic structure. For example. Suppose your piece is in C sharp major. The tonic chord is, then C sharp, E sharp, G sharp. On the other hand, suppose your piece is in D flat major. Then your tonic chord is D flat, F, and A flat. Same doggone chord. Thing is, we write the C sharp major version as C sharp, F and G sharp. Which doesn't show the underlying major third as clearly (in fact, what it shows is a chord with a diminished fourth... which is the same in equal temperament as a major third)(oh dear, this gets so confusing...).
Ideally, in an equal temperament, all transpositions would sound exactly the same. Maybe it's all in my head, but to me at least they don't.