The thing is, I can't imagine how I would superset A1 and A2 exercises in a gym full of people. I can't exactly hog both the bench press and another bar to do barbell rows for 4 or 5 sets of each. Same with military presses and lateral pulldowns, or any other pair of exercises besides one that both use dumbbells. Leaving out the lucky ones who own a home gym, how do you gym rats do it?
When I did supersets months ago, I would arrive at the gym right when it opened, as there weren't many people there at that time. If you're flexible with your time, then maybe just try opting for a time when it's less crowded.
Of course, there are other options, for instance getting creative with your superset exercise selection to do things on the same bar (I feel like you could do this with BB bench and BB row).
It's not that hard. I've supersetted in an ultra crowded gym before. Hell, I've even managed supersets with 4 exercises (not sure if that's still a "superset" but whatever). Grab a db, haul it over and keep it under the bench press. Superset bench press with single arm db rows. Or haul a few db's underneath the pull up bar. Superset pullups with overhead db press.
If you're working out at a recreational/commercial gym, most lifters will be intimidated by you anyway if you look like you even half-way know what the fuck you are doing. "Hey brah, he's doing some fancy shit where he alternates exercises...he must be...like..SERIOUS...don't mess with him, brah!"
This works, but not always for the reason you mention; people are not such asses (at least in my gym..); they can see what you're doing. Just be prepared that one item of equipment will get grabbed, so you just 'work in' on it with someone else, and you might get random extra seconds between exercises. But using DBs is indeed best advice.
I see your point, but I've never had a confrontation with it. I just wanted to point out that it's possible if OP is set on it. Plus, I use the weights just about as long as I would have if I had done straight sets, which is still about half the time the majority of guys will use them, since they often spend 5 min between sets chatting it up with their bros. Not trying to be obnoxious. I workout at a college rec center, so whenever I basically grab any db over 50lbs, there's really no competition for it anyway.
I can't speak about commercial/Chain gyms, I've never had a membership at one. In the gyms(4) where I have trained this is not considered poor etiquette at all. The gym is plenty crowded at times and everyone seems to be able to work together. If someone is using bells, a machine, or an area and I want in I just ask; and it goes both ways. You would be more than welcome to grab the dumbells if you needed them and I would walk over and grab them to get my set it, and on it goes. Just isn't a problem.
Exactly its not a big deal. Besides I know it has already been said but the whole idea of a superset is to do two exercises in around the time it take to do one. So unless you are reracking the DBS in between your straight sets then its not that different.