25 million already upgraded to iOS 5, and 20 million activated iCloud. Looks like developers will have an easy time targeting iOS 5 and utilizing iCloud for their apps.

The bump in internet traffic from people upgrading was very noticeable:
http://www.guardian.co.uk/technology/2011/oct/13/ios-5-update-internet-traffic-spike

ISPs will probably appreciate that iOS is back to doing delta updates going forward. On the Mac running Lion, the full OS 10.7.2/iTunes 10.5/iOS 5 stack was around 1.3GB worth of downloads.