Apple will be releasing the final version of the 3.0 software to exsiting iPhone and iPod touch customers on June 17, with the new iPhone - the iPhone 3GS - two days later on the 19th.
It’s a good thing. Last year - on July 11 - Apple released the iPhone 3G and OS 2.0 on the same day. Between all the new devices being activate in iTunes and everyone upgrading (and thus re-activating with iTunes), the iTunes servers bit the dust. Hopefully by spreading the pain out over a couple of days, Apple’s infrastructure won’t fail this time around.