In my opinion skytime offer a better product than either netjets or skyjet, Admittedly they are a smaller and that may always be a problem for them but they do offer the benefits of both the larger companies but with the added benefits of charter, i.e. you get your guaranteed availability at a fixed from 'anywhere' which is ideal for one-way flights but if you perform a round-trip, you get a true 'charter' price.
The comp i am employed by have a contract with skytime as a back up to our aircraft and the service is spot on.
This comes after the boss was a direct netjet customer who is more than happy with what we now get.
It might not work for everyone and other people may have their own ideas or agendas but skytime work for us.
Not a definitive answer but an opinion none the less.
Cant comment on 328 from a customer point of view.