The bitcoins I have stored on blockchain.info are still spendable even with their web site down because I imported the private key into Armory.
Yes, but i am creating a website that was using their API to manage transactions.
Now I've just bought an odroid-u2 to install bitcoind and do it myself because i don't trust the service. It may be down at anytime.
(By the way, i love blockchain.info.)
UPDATE: And i will probably use my server AND blockchain.info (just in case something happens)