According to the
AP, Apple iTunes servers are having a tough time keeping up with the registration demand. This has lead many iPhone 3G buyers frustrated and without service. Apple Store staff are telling customers to go home to finish the instillation. Home activation hasn't gone any smoother for them, apparently.
Those that need their phone over the weekend may want to hold off until next week.
On the brightside, there's been no complaints on the software side from those who've been able to get their iPhone 3G's actived, so the iPhone 2.0 update seems to be raring along.