From friends experiences... Mixed reviews. The pack themselves, they LOVE... Long term traveling - frame packs absolutely rock. The only downside complained of travel wise - harder to get rides hitchhiking.... But not for the normal "looks like an ax murderer" or whatever type reasons... Frame packs cmostly don't fit in cars. So unless the trunk is like totally clear - there's just no place to put person AND pack. That was the travel complaint.
.... As far as cops and stores and harassment - that seemed more to do with appearance and carriage. Friends with new packs looking like they just walked out of a high end camping store, who carry themself like a "normal" person - usually got left alone by officials, regardless of how crusty their actual person was. The friends that had barely holding together packs, but were themselves cleaned up and looking like college kids - also tended to not have much problem. The friends that look like time travelers from the Manson family, and carry themself like they were raised in Lord of the Flies - that frame pack was like waving the PLEASE! Fuck with Me! Here is your excuse flag, while screaming fuck the police! ... Those friends always had a hard time though, but the frame pack definitely made it harder for them.
So, my answer is - It's not the pack, it's the appearance and ATTITUDE of the person wearing it. Act civilized while in civilized society (their definition, not yours) and they're more inclined to treat you like everyone else.... Don't want to be everyone else, expect to be treated as such. The pack is just an excuse to justify what they would do, based on their eyes judgement alone, anyway. It just makes them take more notice of what they're looking at... You could get the same flack wearing a ton of loud bells. Extra looks for sure, but asked to leave, or whatnot, more about you than the pack.
But hey, judgemental assholes are going to be that regardless, anyways... Right?
Best of luck & I hope nobody gives you shit.
Another trick though - especially with libraries and such - Go Ask! (Preferably without pack, at first) Just ask what their policy is... If they say No packs, it's easier to try to reason them to your side and letting you in with it - Before they're trying to throw you out and you're pleading ignorance. Asking first frequently goes a long way, and reasonable people will often make reasonable accommodations to rules - if given a chance.
