Same here I can receive, but not send. The error message reads;
"The connection to the outgoing server "p05-stmp.mail.me.com" failed. Additional Outgoing Mail Servers can be configured in Settings > Mail, contacts, Calendars."
I upgraded to iOS5 last night, joined iCloud and liked the idea of a @me.com address so signed up. I have never had a MobileMe account. I have and iPad2.
I want to use my new address it's way cool and doesn't get spam (yet!)