it depends on tastes and tea. Most people consider the post-fermentation taste unpleasant, though I know several people who like it.
I think that it generally depends on the level of fermentation. Heavily fermented shu does not age as sheng does, but unpleasant odors vanish with time. They do so also with less fermented shu, but on top of that, some addional "natural" fermentation may supposedly happen.
I would generally say that aging does improve shu slightly by making it more easy-going and smooth, but it is not nearly as notable as with sheng puerh.