you can't really say for certain that your tank's setup is a "success" untill it's run for at least 6 months without any problems.
you definitely can't identify a fish's temperament until it's had time to settle into its environment, which takes a few weeks to be really sure.
if you've acquired juvenile fish, then you need to wait until they reach sexual maturity before you can really decide what kind of personality they have.
--EDIT--
newbies, i was joking in the comparisons previously listed in this spot. please don't use my little jest as actual information.