I've ordered 3 times from Dell, the first time was my XPS420 Desktop, about 6 years ago (which until a couple of years ago was running perfectly fine with stock parts, then they started failing so I upgraded it a bit), the second time for a printer cable (yeah I know, silly D: ), and my third order was my m17x. So far every order arrived on scheduled time, heck my m17x arrived even a couple fo days earlier than scheduled, so I can't really complain about anything. I've even exchanged a couple of email with the customer service, and I can't really complain about that either.
So to sum it up, I'm truly satisfacted by Dell services up until now.