I run three jbj's and have never had any issues with them in the several years that I have been running them.
I also run a tunze mini ato on my 40b which is super awesome for that size tank. It has shutoffs so that it wont overflow and it only pumps in a small amount of water since its the nano version so thats another way it wont overflow the tank. I find the tunze to be perfect for smaller tanks and the JBJ's for larger tanks.
The tunze is a little more money than the jbj but it comes with the pump already and it looks so clean and sleek, even has a holder for the tubing that pumps the water into the sump/overflow so the hose wont pop off and cause a flood. Great quality too, you can feel it's worth the extra $$ just by holding it.