I am a big fan of the Opsaks. I always use one in conjunction with my food bag, which is most of the time a ZPacks Blast food bag (with the cinch top).
I have a trip coming up in 2 weeks, and have slowly been getting some of my food for this trip. I have been keeping it inside my 12 x 20 Opsak, which has been inside a Granite Gear UberLite 10L roll top bag. The Opsak has been sealed shut for about the last week, since I was last in it. I opened it up today though looking for a packet of Emergen-C and wow! I did not smell anything until I opened it up, and when I did...it was like the smells had been waiting to escape! It was definitely a strong smell, and everything inside the Opsak is still in it's original packaging. There is an assortment of bars, some drink mixes, poptarts and some other stuff I can't remember right off the top of my head.
Anyway, like I said, I always use one. I will admit, when I am adding in that 1.3 oz for the Opsak into my spreadsheet, it kind of sucks...but I had rather carry it for a little extra protection. I still hang my food in bear country though.
Does, it work, I dunno...all I do know is that I have yet to wake up to find remnants of my food bag laying all over the place...instead, it is always hanging in the trees right where I left it.
I will admit too though, I do not wash my hands before handling the Opsak, so I know that there has gotten to be smells on the outside too.