I've used glutes as my main site and after over 2 years of pinning them i definately have scar tissue. I would say it is has become much more apparent lately, i didnt used to mind injecting at all but now it feels far more painful than it did a year or two ago. Time to start using a different site, i just cant stand quad or delt inections which is why i use glutes so often.
On a side note often when i bend over to pick something up i sometimes get a pain in my glute that feels like when you hit a nerve, not painful however causes a reflex flinching action
I'm going to start using a foam roller on this area which will hopefully help a bit.