Drilled rotors are considerably lighter, reducing unsprung weight, allowing the forks to do a better job of keeping the tire on the road. Drilling also helps cool discs, and pads by pulling pockets of air across the pads. (Overheated pads transfer heat to the caliper piston, heating up the fluid which causes it to expand and may seize the brake.) Drilled discs also dissipate water better if you get caught in the rain. Drilled rotors on on all the vintage road racers with good reason.
I've had drilled rotors on several bikes, and I can account for over 120,000 miles on drilled discs since 1978, and never even heard of cracked or shattered discs. I have seen lots of rotors that were scored because people don't always prep the rotor when they put on new pads, or let the pads wear too thin, and heat up the rotor. The only disc I've had trouble with is the solid one on my CB500T. I rebuilt the caliper, replaced the pads, adjusted to spec, replaced the master cylinder, and it just won't seat properly, and takes a hulk like grip to get any action out of it. So it's being replaced with a TLS 8).
I've never had rotors serviced by anyone, and don't have any experience with the vendor on eBay, but I have replaced old rotors that were at their min.
My Kawasaki Concours tips the scales at 595lbs bone dry, add seven+/-gal of fuel, 4qt oil, me, and camping gear, and your looking at over 800lbs. Still, it's no sled. The Concours is well known for eating up miles of twisty roads with ease, and I thoroughly enjoy hearing the tire scrub while I'm zigzag my way through the Smokies. So those brakes get a good workout, and never failed me.
I know, you really didn't ask for all this, but dammit I felt so stupid after that "Bake Swap" posting.
