The only problem I ran into with it was the first time I used it, the paint was coming out under the nozzle making a mess, I know a few others had this same problem. Lately that hasn't happend so maybe it was a problem Krylon fixed.
On the dull and shiny I've noticed that more when I use it over primer or another paint. The thing I really like about it is you really have to try and make it run, I've been in a hurry and been impatient several times where I know another paint would have run but the Fusion goes on perfect anyway.
I have decided it is more sensitive to cold and humidity though, but I can't prove it, just a theory I'm developing.