While I have never owned one, I have been doing quite a bit of research as I would like to get some better flow in my tank. I narrowed it down to really two options a Vortech or a Tunze 6055 and an Aquasurf.
Looking at the forums, there seems to be a very sharp line on the Vortechs, people either like them or they hate them. They do seem to have a lot of "issues", so I decided to steer clear of them. You may want to look into a Tunze setup instead, they are not perfect either, but the customer service is top notch IMO.
Allen