We bought one of those Mosquito Magnet style devices about 6 years ago when we were living in Qld. Fiendishly expensive. The theory is great - lights and nitrogen gas and baits to attract the mozzies. Unfortunately in practice it doesn't work so well.
Two main problems. 1 is that it also sucks in moths which clag up the fan blades and cause it to stop. The cleaning is a pain. 2nd is you need to position it just right so the nitrogen will flow downhill and attract the mozzies, but also attract them away from your BBQ area. So that doesn't work at all when your BBQ area is in the lower part of the yard - it just attracts them to you. The gas and trap should actually be seperated, but with the ones they sell, they put them together on a stand.
I have a friend who actually traps mozzies for scientific study !! The theory behind these type of traps is sound, but he does not hesitate to admit that there is a lot of art in getting the positioning just right, and exactly the right attractants for the mozzies in a particular area etc. It is very difficult for domestic users.
I went back to the humble mozzie coil. Cheap. Easy to operate and I actually quite like the smell.