Here's what EWG has to say about it:
http://www.cosmeticsdatabase.com/ing...ngred06=725860
It looks fairly safe, but it also looks like there haven't been many tests done on it, so...
Personally, I'm wary of spraying anything on the yard. If you're a gardener, you do a lot of work to build up the soil. Do you really want to be spraying an insecticide that could be killing your insect helper-friends in addition to the mosquitos? That said, if you're spraying your family with DEET every day because the mosquitos are so bad, I might consider it.
Are the mosquitos always bad in your yard? Could you plan outside time around times of day when there are less? One great idea (if your yard isn't too large and you have an outdoor outlet) is to set up a fan outside. Mosquitos can't fly well in wind, so if you stay close enough to the fan, they'll stay away.