there is little doubt in my mind that on many ranges, in many range sessions, it's clearly going to be a pain in the tuckus that will slow down your range day.
It might be, but switching an upper is so darn easy it's hard for me to imagine having a hard time even with a million distractions. I suppose if I could hear the footsteps of killers walking upstairs to shoot me, changing the upper might get nerve wracking, but range noises have never done that to me. And I'm the type of tenderfoot shooter that flinches when the first shots go down range.
The only problem I have ever had is that the range masters at my range want to watch to ensure that I am not doing something that will endanger those around me. Of course, I normally only switch once between calibers. My SD handgun brush up involves shooting 22lr, two handed, left and right handed (altogether about 180 rounds), both from the trigger at half cock and full cock. Once I go through all that, I switch the uppers and then put around 30 rounds of 9mm downrange, and then I quit.