Well, I don't really know any weaknesses, but I can tell you that I love mine! I have a 1995 SC400 with 298,000 miles on it and still purring like a kitten. It was the best money that I ever spent. The only thing not mainteneance related that I have ever done to it is replace the radiator about a year ago, that's IT!!!
Side note: I do use Castrol Synthetic oil