First of all, Thank you everyone for your kind comments. I very much appreciate it.
So far, it seems that Blockchain.info is quiet safe. As long as I understand, blockchain.info does not hold any bitcoin and when the website is abruptly shut down, I can retrieve my coins using open source software with a paper wallet backup.
Trezor looks same in this sense. Trezor provides a seed (consisting of words) and does not hold Bitcoins of users. However, in case Trezor's firmware signing key is hacked and users do not notice it before updating the firmware, there is a chance that a private key is stolen.
For this reason, I do not see any advantage of Trezor over Blockchain.info.
By the way, is there a chance that a private key stored in blockchain.info can be stolen by hacking or unexpected events?
You need, need, NEED to have the paper wallet backup, though. If you haven't gotten it from blockchain, you're not protected.
And treat it as a HOT wallet. Eventhough it is a paper wallet it is not secure like one you create offline properly it is stored on blockchain site.
So remember that as you put BTC in it that you should not treat it as true cold storage. I'm afraid of it people thinking they have a secure paper wallet when it still is not a true cold wallet.
Technically, though, paper wallet in this sense is just a backup. Though I guess you're right in that newbies may not understand the difference.
