Remember a few things:
- Apple doesn't have as much experience in Web Apps as, say, Google. This is a premium service though, and we can't excuse poor quality. It should be working soon, or they'll revert to .Mac (PR disaster, but it's better than having lots of customers without service -- or is it? This is Steve)
- This was made on a strict deadline. It had to be at demo-able state by WWDC, and had to be out to launch alongside the iPhone 3G. They may have had to rush certain bits, which will be fixed after launch. They may have discovered bugs at the last minute, and had to update things whilst launch preparations were ongoing.
- Apple's .Mac servers probably never experienced this kind of load. Hopefully they bought a few more for this service (Push needs a permanent connection to the client. With 3 or 4 devices per user, that's a lot of stress for the servers). Apple may not have anticipated the load they're getting now.
- Web Apps can be pretty complex, as they have no strict structural requirements. And this is built off SproutCore, which I don't think has been tested extensively under heavy load.
It's only 7:30am in Cupertino. Steve's probably using his iPhone to figure out where he can buy a Mace at this hour, ready to storm the .Mac offices.