Wasn't that bad. Took about 15-20 minutes per hole. I probably could've done it faster, but I'd rather take my time to drill it than to increase my chance of cracking the tank.
The bits weren't that expensive at all. Got it from a guy on ebay that is in china or hong kong. Took a few weeks to get them but well worth it. Used the bits on a few tanks and glasses already and so far the bits are still in great shape.