I find it highly unlikely we'll get another "launch day", or saturday delivery for that matter. I'm sure the coordination of getting everything out on the same day, and that day being a saturday, cost apple a pretty penny. There's no real reason for them to do that with the 3G, since they've already had their media "launch", and as long as these things go out in late april no one really has a reason to complain.
I think the only reason they did the saturday thing with the non-3G was because they originally said "late march" for the release, and when they couldn't hit that, they switched it to be the earliest possible calendar date they could reasonably hit. With the 3G they'll ship when production is ready, and I doubt delivery will be as choreographed as it was with the initial release.
Around the 24th sounds like a good guess though.