Its a popular distro...

Ubuntu are of course aware of the problems, its simply a load matter. There servers can't handle it, unfortunately its stopping people from getting the amazing new OS in all its glory (i tried it, it's grrrrrreat)

There is now a mirror list up at the main site as they've shifted things around by the look of things to try and cool off the release.

Fiesty is available here http://www.ubuntu.com/ (USE A MIRROR)

Or get the bittorrent http://www.bittorrent.com/users/zizazat/torrents/Ubuntu_7.04__Feisty_Fawn__Beta/6e15fbbaa0fc1024886c37da68010f7f930663bc

and update it to using the builtin package updater.