Well, given that most of the gamblers here talk about KYC.
I second that the lack of good support representative isn't a good impression. It's the reason why some gamblers are staying on a casino because of the friendly support, admins and moderators.
And that gives them the idea to make good promos and bonuses for those loyal customer that are staying with them. We can't blame those gamblers that go from one casino to another if they find the ideals of these factors.
Facts. Honestly, KYC isn't that much of an issue sometimes, it's just that the way they ask for it is kind of dumb and stupid that users bloody hate it. Asking for KYC when withdrawing, asking for KYC when originally it wasn't there, those kinds of things are the ones that are irritating but having KYC stated in full black and white at the start? That's pretty agreeable since I can just leave the site and choose to go to another casino.
As for customer support, well that's always a number one kind of thing. I'd always want an agreeable customer support, one that doesn't just half ass you when you're trying to inquire stuff.