Apple officially announced that the company sold 1 million iPhone 3G S over the weekend. Earlier we reported about Piper Jaffray analyst Gene Munster estimating 750,000 units.
In addition, 6 million users have downloaded the new iPhone 3.0 software in the first five days since its release.
Now there is an official reason behind the activation delays. To activate 1 million units at the same time is hard, but Apple has seen it coming as they offered pre-orders ahead of the launch day. Additionally the same issues happened in 2008.

Anyway the new iPhone has had a huge start despite not being revolutionary.
Via this Apple announcement.

On a side note:
Apple is apparently not consistent in how to call the new iPhone. In the Apple store the new iPhone is called iPhone 3G S. In this press-release Apple calls it iPhone 3GS without a space. Message to Apple: Get consistent or find a better name next time.