Surge protector helped me discover bad wiring at home -- neutral and line swapped; should I be concerned?
Yes, you should care.  The electric code is generally designed so that it takes two independent failures before you get shocked.  In you're apartment, one is already used up by the line and neutral being flipped, so you are closer to a dangerous situation.  If all else works correctly, this one error shoudn't matter.  As Dirty Harry would say:

&nbsp;&nbsp; Do you feel lucky?  Well do you, punk?

You don't say where this is, but in most jurisdictions this is a serious matter.  I would first politely point out the problem you found to the landlord, and give him a chance to fix it.  If you need to convince him, point out how this is a serious liability to him if you or anyone else gets hurt, and that his insurance company may refuse to pay in case of electrical fire.

If he still refuses or tries to tell you it's OK or something, then you should take further action.  Talk to your local electrical inspector, and ask if what you found is OK.  It won't be.  Then tell him you brought this to the attention of the landlord and he refused to do anything about it.  Most likely the electrical inspector will now have steam coming out of his ears.  He'll take it from there, and the landlord won't like it.

You should absolutely not have changed the wiring yourself.  Here in the US, for example, that is illegal for someone who is not a licenced electrician to do, and/or would require a inspection afterwards.  You also had no right to do this without the landlord's approval, whether you were fixing something or not.  You now own the liability.  Don't mention anything about the modifications you made.  Only talk to the landord, and electrical inspector if necessary, about the remaining outlets.  And don't modify any more wiring.