I think that's possible both ways between blockchain.info and qt.
If you are talking about using a debug function in Bitcoin-QT, I have not found this easy to do, and the new investors that I am trying to convince are even less computer competent than me. The blockchain.info function of dragging a file into the square and then typing the password would be something than anyone can do. That function does work for the wallet.aes.json blockchain.info wallet backups, but it would be nice if it also worked for the wallet.dat files as it is advertised to do. It would be worth their time to try to fix this bug.