While being able to open carry a firearm is your right in many places (more specific info here), using this right to scare the hell out of people is always a bad idea. Personally I don't open carry anymore. I choose to carry concealed for many reasons, mostly to not alert people that I am carrying (the element of surprise is always something you want on your side), there is less of an issue with weapon retention, and because I am in an urban area most of the time, and while it may be legal to open carry in many urban areas, it tends to terrify people, especially in our current political climate.
In urban areas there are a few good reasons to open carry. I have yet to see a convenience store worker NOT open carrying around Miami and this is probably a good thing when you see the clientele they have to deal with daily. I've seen a few people open carrying in my city, in both cases they had shirts on identifying them as working at local shooting ranges (pretty good publicity IMHO), and we've got a guy who walks his dog around our neighborhood every morning while he is open carrying (it's his right, he doesn't seem like a whack job, and it probably makes our neighborhood a bit safer).
In rural areas it is still quite common to see people open carrying. With people who work on ranches, a firearm is pretty much part of their daily carry. During hunting season, it is quite common to see all manner of firearms being carried about, to and from vehicles, on trails, into the local cafe for breakfast, etc.
I think pre-planned open carry events are a good thing. These events are usually publicized, the purpose is to educate the public about their gun rights (the people who participate in these events are generally very knowledgeable about guns and gun rights and happy to share their knowledge with others), and having a whole bunch of people open carrying at the same event is actually less intimidating than one random guy in body armor open carrying to make a point to the jittery public.
So while it is your right to open carry in many places, in the current climate of mass shootings, it behooves gun owners who want to open carry to be tactful, to know their rights backwards and forwards (this will come in handy if--more likely when--you get arrested), and to be aware that while you may absolutely be in the right, the response from everyone from the police to the general public can be iffy at best.