I'm convinced that I have a good copy. Opitical quality is comparable to both the 35L and 85L if you ask me. I've previously owned both. Color, contrast, OOF blur, and AF speed are all on the level. AF is not as fast as the 35L, but quicker than the 85L MK I. After extensive shooting, I found it to be not quite as "razor" sharp as the 35L or 85L, but it's still sharp. I used a filter the whole time I shot with it in Africa, so that may have degraded optical quality somewhat. Knowing what I know right now with the focusing issues, I'd hold off on buying this lens for the time being. With more and more people coming out of wood work claiming they're having focusing issues, including those who said they have a good copy and are now claiming otherwise, there very well may be a problem with this lens. It could also be paranoia or buyers remorse for some of these guys. When you pay this much for lens, you expect it to be completely trouble free and I don't really blame them for painstakingly testing their lens to point where they finally do find something wrong. I'm monitoring the situation closely.
For the most part, I just take pictures with mine. Though it appears to work as advertised, I'm now constantly on the look out for the dreaded back-focus monster. It should strike any day now... 
With that said, I voted Canon should address the issue. I know I'd feel a lot better about it.