I am a fan of the MT-66 as well. I have used it on 3 bikes and always liked the ride and wet or dry grip. Around 9-10K miles on a similar weight bike on the rear, more like 16K on the front.
Pirelli may own Metzeler, but it does not mean they own the problems. Pirelli bought Metzeler to keep Michelin from buying it and shutting it down. Metzeler has had well documented quality control issues for years, and I won't recommend them to anyone, but I would not hold it over the parent company's head. I hate fucking Dunlop motorcycle tires with a passion, but I'll still buy a Goodyear car tire. I've heard too many mixed results from Shinko to have an opinion, and I've never bought any for that reason. I have Michelins on my Road Star, Continentals on my SV, and junk on my XS that will eventually be raised white letter S-11s.