If you are meticulous in you preparation of the unit and the initial setup, it goes fairly well. I had a hard time setting it up myself. I gave mine to a reefer friend who was much more patient than I to use (my tank was down after a crash). He got it setup right away and hasn't had any issues with it. It's been about 7 months with just consistent results.
I'm going to replacing the one I gave to him with one for myself - I think it's agreat product, just not a perfect product. For somepeople its a very frustrating device, and those people, rightly so are vocal about their frustrations.
But there seem to be a large number of people who have the unit working without the frustration and are really enjoying it.
I think preparation for maitaining the unit is key and making sure you have all the different tubings, caps, and a motor or two in a spare cabinet is kind of a necessity.
If you can get a deal on one, and you know that Focustronic products can have some quirks and you are okay with that - Then go for it.
Dave B