I would have to agree with Splat on the inducing panic phenomenon. I admit, my CCW instructor told us that in his opinion, while legal, open carry is a bad idea "in this state". Generally though, it's pretty widely ignored and I've not had a bad experience yet. In my city, the police actually circulated an internal memo indicating that officers are -not- to trouble open carrying citizens unless the individual in question is acting unnaturally or committing a crime.
Obviously that statement is pretty open ended as far as giving the officers power to detain you at their discretion, but the memo did convey the message that open carry is uncommon but legal and it's not grounds for arrest by itself. As far as panicked citizens calling 911...it has happened before (in Ohio, well documented, and usually no long term negative effects for the carrier in question) but it's far from common. The practice of open carry is still fairly uncommon but I do occasionally see someone with a gun and no visible badge. Unfortunate or otherwise, I believe that the average unaware citizen simply assumes that the nonchalant people wearing guns without uniforms are somehow authorized to do so (you don't need authorization in Ohio for loaded unconcealed carry, unless you are in a vehicle).
The worst reaction I've encountered is a twitchy frightened stare, the givers of which I prefer to assume are up to no good in the first place.
Anyway, on the actual topic - seems like most people agree that a thumb break or internal latch aren't really necessary. I more or less felt that way in the first place but it never hurts to get a round of opinions. Thanks!
Sharp as a cue ball...but moving faster.