Generally, I'm all for things that limit emissions and improve safety. I always thought they were a PITA, but couldn't really be that much worse than the ones I see people use at the track usually.

I finally picked one up because it was all they had at the store, and holy shit those "safety tanks" are a nightmare by comparison. They spill so much fuel and after only a couple of years the seals on mine have gone bad and leak even more. I still would like to add a flame arrestor into the necks, but it amazes me at how awful they are.

I wholly understand why they exist and what all the safety features are for (preventing fuel from spilling if they're tipped/dropped, releasing fuel vapors, etc) but they seem utterly useless when I inevitably spill at least half a cup of fuel per 5 gal, just due to how poorly they're made.