I've never been able to do a clean break. It ALWAYS follows the score line for about 3/4 of the way, then curls left or right after that. Well, OK, I've done it a couple of times successfully but more times it went like that instead of successfully. I have no idea what I'm doing wrong. People keep telling me that it's easy, but I truly do suck at it. So don't ask me.
I do have a glass cutter/scorer thing you could borrow if you want but they're only about $12 at Rona/HD/etc. And of course, who's to say my cutter/scorer thingymabob isn't the problem itself..