Is there any reason to prefer one of the following notations over the others or is this simply a matter of preference?
map toLower "FOO"
fmap toLower "FOO"
toLower <$> "FOO"
As an aside: I realize that <$> is the same as `fmap`. Am I right in the assumption that map is just a less general form of fmap?
As you say, map is a less general form of fmap. If you know you have a list then I would use map as it makes the code clearer and if you make a mistake the error message is likely to be less confusing. However to a large extent it's a matter of preference.
(<$>) is the same as fmap. Until GHC 7.10 it wasn't exported by the Prelude so wasn't available by default - but even with older GHC versions it's easy to import from Data.Functor or Control.Applicative and these days it's pretty much the standard way to do this.
I agree with Ganesh that map is clearer for lists. I use <$> over fmap, unless it is partially applied. So I'd use fmap reverse to declare a function that reverses all elements of some functor but if I have all the arguments available (e.g. if I'm writing a line in a do block) I tend to use the operator form: reverse <$> f x
