Yea blockchain.info is definitely a solid wallet, i think its safe to use it up to 10 bitcoin.
After that you need offline vault.
No, it's not. Blockchain.info is not a secure online wallet. Now, the only secure wallet which I can think of is GreenAddress. Blockchain.info seriously flawed. It may have been a secure online wallet earlier but not now.
It think there is no Security in the whole Network. I think if u wanne to be for real sure that ur Coins Stay where they are. Install an Wallet on an Offline PC like Core.
regards