i don't know if GC impacted them as much as how their store functioned.
one of the sales guys used to play guitars at super loud volume, and he encouraged others to do the same, so whenever i was trying to actually test amps or cabs, i couldn't really get an idea of how they sounded. only once in over 20 years have i managed to buy something - not even when using cash - in under 40 minutes. the one exception a bag of picks i paid for with cash, and it took about 25 minutes. there were always issues, someone would need to confer with another sales guy or call the manager, their own system would confuse them, something had been changed in the system. yet i could trade a guitar at guitar center, pay for one i had had my eye on, and be out the door in 20 minutes with no weirdness at all.
we had a layaway at hollywood sam ash, and when we went to pay it off, they couldn't find the guitar for an hour - it turned out to be somewhere it wasn't supposed to be. the case for that guitar was so lost that they had to call us after they found it days later.
once, we traded them 3 basses and guitars to pay for a guitar my husband fell i love with, it took about 2 hours - the store had been closed for some time by the time we were done.
i could go on and on - oh, wait - i did! - with stories about sam ash hollywood. according to many musicians i've played known, my experiences were pretty typical.