Yeah Opuntia microdasys is definitely one of those good/bad kind of cacti, but while its glochids are pretty bad, there are a couple of other prickly pears that bother me a lot more when I get some of their glochids in me, the worst I would say is Opuntia santa rita, generally much longer glochids so much harder to get rid of once they have struck, the other one is the cow tongue prickly pear, maybe I have some specific sensitivity to that one, because that one does at first glance not appear to be that terrible when it comes to glochids, but man....
As people have already said about O. microdasys, the plant if planted in the ground and provided with just a little extra water, it is prone to take over whatever space it is given. In a large clump/grouping they do look awesome, but they will crowd out any other low growing plants. If kept in a pot it tends to need a larger pot quite often and if you do not pot it up regularly it is prone to what I have started calling colony collapse: it will get to a point where it will just start shedding pads and more pads and really nothing you can do except pot it up will stop that, and while a good pruning will get it to growing more regularly again it will start looking pretty ratty, so keep that in mind when growing this in a pot. Also this particular prickly pear sheds pads very readily so handling it a lot will probably cause quite a few pads to come off it, and while it will grow plenty quick to recover from that, it is something to keep in mind.
Anyway as to separating plants: I use a variety of salad tongs and other grabbing tools and usually wait for the pot the be completely dry so I can shake off a lot of the soil (especially when it is my own pumice rich mix) and then try to gently pull things apart, if that does not work or there is too much soil left I will try to wash that a way, but in the end, if easy separation eludes me, I just gently tear them apart and then let them sit in the shade for a few days, to callous over any damage areas.
I usually separate plants that will look better as single stemmed/trunked specimens or if I am trying to propagate, most of the time when it is just about getting a plant in a bigger pot, I do not bother. However, my main focus is growing plants in the ground rather than in pots (I just have more potted plants than in the ground plants because I am a bit of a hoarder and am generally out of space), so I am usually just waiting for a plant to grow big enough to survive better in the ground or for space to open up. So part of the decision on separating or not really depends on what you want from the plant you are dealing with, but with Opuntias the other thing to remember is that just about every decently sized pad is the start of another plant, so if you want to create another one the hassle of splitting can easily be avoided by just taking a pad or two and sticking those in the soil.
