> But don't allow issues to go stale. To really wow customer service, reply as humanely quick as possible, especially for existing customers.

As a customer, the absolute worst possible thing for me is to be left in limbo, not knowing if my problem will be fixed in the next minute, hour, day, or never. While I may not be thrilled if the answer is "never", at least at that point I can move on and know that I'll need to solve the problem some other way.