Yes it is a big rollout, and an assorted problem would be understandable, but this does not seem to be a small problem, but rather a widespread and pervasive problem.
If the interest in the iPhone was significantly greater than expected, I could also see that there would be problems, but when Apple is putting out press releases that they expect to sell 3 million phones this weekend, at least 1 million of which would go Friday night alone, and Steve Jobs in an interview yesterday was inferring that he thought they would sell out yesterday, then I don't think it is fair to say that they are overwhelmed, rather their planning was just underwhelming.
They expected millions of activations in the first 24 hours, that is what happened, and they were completely unprepared for it.
Had I gotten the phone for $99 then maybe I would be more patient, but for $599 I don't expect to have to wait until Sunday to get a phone I purchased on Friday, activated.