Knife laws can be tricky and change all the time. For instance, even living and carrying in Indiana, I had no idea that that laws on the books changed a couple years ago. For the longest time, pretty much everything was permitted except for autos, daggers, and throwing stars.
Well, I guess the popularity of assisted openers got law makers' attentions. Thankfully, for once, rationality prevailed. Instead of banning an entire genre of incredible tools, they just struck down the archaic auto law. Now I can carry pretty much anything except throwing stars (still a silly law, but I'll take what I can get). I walked into a sporting good's store a few weeks ago and walked out with a Kershaw Launch 2.
The funny thing, now that I CAN purchase autos...I dunno what to do with them

The Launch is a really well built knife for under $100. Snappy, good lock up, nice finish on the steel and LIGHT. But I can't find a niche it fills. I've been using it as my "dress knife". It's so light and sleek that it fills the role of being a handy cutter while out and about.
I digress
I think so much of "legality" is going to come down to how much hassle you want to go through. Most of the police officers I know (friends and customers) aren't going to bust my chops if I use a knife that is technically over the legal limit (if there were such limitations in this state) if I am being responsible. Also, most patrons out and about aren't going to care if you aren't being an idiot.
I have been carrying a ZT 909 on me the last few weeks. It's a beefy knife sporting nearly 4" of blade. I used it in a sit-down restaurant last weekend to cut my daughter's drinking straw down so that it wouldn't tip her cup. I got zero looks doing it. That was mostly likely due to the fact that I didn't sweep the knife out giving the flipper a push with mucho gusto and a satisfying THWACK. I palmed it, pressed the flipper down enough to overcome the detent and fanned the blade open quietly with my other hand until it locked. No need to draw attention and bothers others even if it is within your rights.
I don't get to big cities that restrict carry much at all. I've been to Chicago once (not for me, but I'm glad I've seen it). I didn't think twice about the knife laws. I was at a convention, not on the street. I don't even remember what I had in my pockets. Probably a Spyderco Endura or something lightweight but capable. Never got a look, but then I never left the building more than 3 times over 2 days and was always herded into a gaggle of sales reps sporting dockers and polos...not really the type that gets a lot of eyeballing by police.
I've never been to New York, but I'll be sure to pack nothing more than a slip joint when I do go.
I did spend a week in Ireland almost 6 years ago. I knew that Euro knife laws can be more strict, or at least perceived as such. However, I also knew I would be spending my time in quaint villages and not in the big cities. So I researched the laws as best I could and packed a SAK Explorer. I put a lot of thought into it. It didn't lock open, wouldn't open with one had, and it LOOKED like a tool. 4 springs thick with a magnifying glass being one of the tools (how scary is a magnifying glass? exactly

).
Even at that, I don't think I used the blade once during the trip. I think I cut a few strings/tags off things for my wife and used the screw driver to fix her camera. No one ever saw it, and it never was an issue.