Mosquitomagnets work well... when they work. Good concept, but they're built like cheap toys - total junk. I've owned three of them, the Defender (corded), and two Liberty Pluses (cordless). The Liberty Pluses are very finicky, keeping one running is like having a second wife. The Defender is more reliable but plan on doing yearly maintenance (disassembly, cleaning) to keep it running. There is info on fixing these things on the net but it's so scattered, I started a forum at
http://mosquitomagnet.freeforums.org/ to try to centralize things.
You can save $ by getting Octenol refill kits on eBay rather than spending $20 a box at Home Depot. Also plan on going through a 20 lb. tank of propane every three weeks. At one point I had two of these running and between the mosquitos and the Weber grill I was spending a fortune in propane.
I've had better than average success with MosquitoMagnets, but I no longer use them. The first reason was the hassle and cost of running them. The second, and perhaps more important reason, is that even if your Mosquito Magnet is one of the "good ones" and catches thousands of mosquitoes, it can't catch every single one. You still end up getting bit.
Our strategy now is to use several of the blue OFF Clip-on repellants whenever we are in the backyard. We leave a few on the patio furniture, maybe clip them on during yard work, and they really work well. In the evenings we'll light up 2 or 3 OFF power pad lanterns in addition to the clip-ons, and we literally have zero mosquitoes. I haven't compared the cost of the OFF system to the cost of running mosquitomagnets, but I'm pretty sure it's less, and even if not, it seems to be a better technology for dealing with mosquitoes.
Good luck my friend!!!!