I've had pretty good luck making glass cups out of bottles through this method. While the break is rarely perfectly straight, it is usually good enough to make a glass out of it.
The comments from the Corning Glass Museum point out that a fine flame works better, and I've used both kinds of torches. The fine flame does seem a bit better, but a plumbers torch works too.
If the bottle has lots of bumps in it and looks irregular, it will probably cut weirdly.
Make your scribe mark straight. The crack seems to follow its directions, so if you scribe at an angle, cut will be at an angle.
I haven't used Dan Rojas's technique since I haven't bought the equipment. His solar oven materials are excellent, so maybe this is a better method too.