Every time you call a user a luser, idiot, or the like, you show your disregard for the customer. While joking around after hours may seem like fun, it will influence the way you see customers, and therefore the way you treat them. Finger point at how other departments are not doing their job. If you have constructive criticism, or some way to help another department, then express it. If you're looking to pass the buck, or boost your ego by putting another department down, then grow up, and keep it to yourself.
Service is king.
Customers will stay on hold for only so long before they'll leave. One thing that amazes me about some ISPs is that there is no hold time for sales, as new sales are important, but a hold queue for tech support. It's much easier to keep customers then to find new ones. Poor coordination across departments. The Dilbert effect has killed many companies.