No flats last summer for me using thornproof MTB tubes, but they are heavy.
I used to get a flat from a friggin' goathead almost every ride on at least one of the bikes (me and wifey). With the added weight, I may ride the tiniest bit slower. Maybe I don't make it right to the top of the odd hill. I'd rather be riding slower than stopped changing and/or repairing tubes, though.
I tried slime tubes in my wife's bike. They worked ok, but we still ended up spending a fair amount of time adding air to the tube when she did get thorns/goatheads. Pinchflats with slime tubes are darn messy, too...
You only let that happen once, which then leads to paranoia about air pressure.
Stan's seem to have a good reputation in the market. If you're worried about the weight, perhaps give them a go. I might try them myself later in the year (financial justification pending
).