I drilled mine! It wasn't too difficult. I got my glass drill bit from glass-holes.com. They have a video on their site which shows the process, too. It's pretty funny to watch... they put in amusing background music and sound effects.
A couple other tips... it's true that once you have the hole started, you want to stay perpendicular. However, it's easier to start the hole with the drill slightly angled, then once you've got a groove going very slowly bring the drill back to perpendicular while drilling. As you drill, don't push down at all... just let the weight of the drill do all the work.
Also, if you have access to one, it's very helpful to have a drill with a torque adjustment. I use it any time I'm drilling anything brittle. The torque adjustment causes the drill to stop spinning when the set torque is exceeded, rather than jamming and shattering your tank.