Fluval Fanatic For Fish Tank here!!! I have a 403 for my 40 gal well planted and really have not had any problems with it or any other Fluvals I have own in the past.
As for the primer I used to have problems but noticed I had some Java Fern stuck on the inlet and was stopping the ball from blocking the inlet tube which will cause a backflow into the inlet tube and then when you restart the pump the water would start flowing in reverse. But I make sure the ball is cleaned before is start-up and everything is fine.
The spraybar seemed to be too strong of a current fro the 40 gal. so I made three more lines of holes just a little larger than the original one row of holes. This lowered the force that the water would exit the spraybar and also prevented the nearby plants from getting bent over from the force of the water.