As others have said, "good" leather is totally subjective. Some people don't like veins, others love it. Some people don't like shine, others love it. For me personally, good leather means that it's thick, matte, smooth (minimal crackling), and so soft that it collapses into a puddle.
You know, it's so interesting. I have no idea how or why 06 leathers got their "bad" reputation. Because every last 06 bag I've had (and I've owned six) had incredible, soft, smooth leather. In fact, the best leather of any bag I've had, regardless of the year, was my 06 BI City. It was like buttah. I think that generalizing from year to year is completely useless. Each bag was made with a different hide, and animal hides can vary just as much as human skin can!