Pages “Send via email” doesn’t work after upgrade

You may just need to wait.

I transferred my MobileMe account to iCloud on iOS 5 launch day. I encountered the same issues that you seem to be having in that when I tried to use the mail app on iCloud.com it gave me same error message as you received. When I tried to turn mail and notes on in the iCloud system preferences, it just hanged on 'starting'. All other features were working correctly.

I just trumpet it up to high demand on Apple's servers and decided to wait. I just tried now and my email is working from both iCloud.com and mail.app.

Not directly to iBooks, no. But you can email it to whatever email account you have set up on the iPad. Then, using the Open With button you can send it to iBooks or any compatible app on your iPad.

I do this all the time with whitepapers I find on my work computer that I want to read on the train. Alternatively, I send my self a link to the file if it's not behind a paywall or lead generation form.