i say they fall under bad.
they arent ugly when they work, actually quite the contrary. i think fog really sets a viv off. i built a couple that were mediocre to decent, but with fog they seemed to be awesome!!
the problem is they arent good either. i bought 2 units. within a few months i had taken both of them back for replacements. within a few more months i had taken one of the replacements back for another trade in. after many weeks of waiting and agonizing over the poor quality of these things i decided to scrap them. my LPS aint cheap neither. $120 worth of headaches and pissed off.
the bad is where they fit in. see previous for reasons why
right now im trying out a reli-on cool mist humidifier from WalMart. it was $28 and i think ill get the plumbing for it for under $10. for around $40 i should have a fogger that can run more than one tank. right now i dont have it hooked up in a tank, but it produces 10 times more fog than the exo terra.
ill put a journal up if i can succesfully document the process of hooking it up.