XTR gets into the boutique tip with their rotors. They offer a 140mm rotor, tiny by many standards, but plenty for lighter cross-country riders if they run it on the rear wheel only. The 160 and 180mm rotors are more conventional, but sport their own size-specific, lightweight spiders.The XTR disc brake rotor comes in 140, 160, and 180mm sizes. All mount to Centerlock disc hubs only.
Strengths: Light, easy to install, sharp looking, stay straight
Weaknesses: Price and availability, the centerlock standard is good but unnecessary
My rotors are actually the RT-79 which are almost identical except they have a slightly heavier spider. I've had these since the spring and have had no issues whatsoever. If there is ever rubbing it is from one of the pistons that doesn't retract very well, but the discs have been straight since day one. It's my first experience with centerlock and with alloy spiders on my rotors. I have to give both high marks for the quiet operation, easy install and respectable weight.
As for the centerlock standard, as a whole it might save unsprung weight, especially considering that you are using an alloy lockring instead of 6 steel bolts, and there is less material in the mounting interface. But the standard is a minority that didn't address any kind of problem with 6-bolt, and that makes the high price and low availability of these rotors sting that much more. I was lucky to find them being auctioned.
I know my Gothics often used to rub with each revolution of the wheel and I hated it, though they looked nasty and stopped like a cat on velcro.