I bought my F-2 from the same Calumet in Santa Ana, actually, and I went back recently looking for the F-5XC (which I ended up ordering online because neither Calumet or Samy's had it - Samy's in-store prices are ridiculous anyway.)
The reason I'm replying though is because I must have talked to the same guy - he was absolutely convinced that canvas was terrible and recommended away from the Domke bags. It's nice he's honest about his opinion, I guess, but I agree that he's wrong and I don't understand his position. Especially since the Domkes they had were among the most expensive in the store!
I was set on the F-5 already, but I asked him what he suggested anyway and he told me he's been using the same Tamrac bag for 20 years, and that I should really be looking at the nylon Tamrac bags. So he wasn't pushing the unimpressive Calumet branded bags (which probably have a much higher profit margin,) at least. I do actually have a Tamrac bag and it's not bad - similar in concept to the Domkes (not over-padded, etc.) but not made as well or as well thought out. The newer version of the model I have has had excessive padding added, actually. In any case the point is that the guy was giving his personal, biased opinion about the bags, because he only has experience with his favorite bag of 20 years.
Anyway - I just had to chime in because I happened to talk to the same guy at Calumet. If you're in the area, Samy's has a better selection of Domke stuff, but I wouldn't buy anything from them. They jack up the prices in-store. But they're good if you want to see for yourself what a bag is like, or to bring your gear in and see what fits.