You're right, you will probably be getting angry calls from him every other day if you are pulling any real amount of current but there still isn't anything he can legally do about it, depending on your specific lease and any loopholes included I suppose. If you are running a farm out of your apartment, he could probably get the fire marshal to come by but as long as your setup isn't unsafe, they can't really do anything either. No law against having computers.

If he does resort to those sort of "guerrilla tactics" like flipping breakers or otherwise interrupting services to your place, you can try to get evidence of him tampering with your power and have a pretty easy to win lawsuit against him. I personally live in a duplex though so the landlord can't get to my breaker-box without me letting him in.

Just throwing the idea out there since it has been working great for me so far.