for one, it will never be as secure as bitcoin, but I suppose you mean practically rather than theoretically; 'who cares about a few thousand when we're working in the billions' kind of stuff. Then there's the factor of relying on the end user to control their security via a passphrase v.s. a file on their machine that needs to be backed up, can be lost, and can be stolen.. Now we're into the juicy stuff.. totally different security models; cracking passwords v. s. hacking machines.. at the end of the day this depends on the end user and their habits - apples to oranges on that front.
to answer your question:
1. never. I have had bitcoin for nearly 2 years and never lost or stolen any. I have had nxt stolen.
2. after 2-3 years. once it has had time to mature, hackers push the limits of available technology to attack it, and it's value hopefully grows to raise the stakes.
Thank you for your answer.
As far as I know, there is already a third-party client, Offspring, which offers the same wallet.dat file as in Bitcoin.
And, the official client at a later stage will also offer an option of brainwallet or wallet.dat.
So that part of user-end security becomes irrelevant. I believe your hack happened due to a weak password. Well, that's user-end security and Bitcoin wallets are regularly stolen with keyloggers as well, like you said, at the end of the day it depends on the end user. In light of that your 'never' in the first answer might change if you choose the same user-end security model as in Bitcoin with a wallet.dat file.
What I meant by security is the security of the algorithm, security of the network. So you're giving it 2-3 years to mature, as far as I understand. Fair enough.