I've followed Kiper's work for many years -- at one time much more closely than I do now. I actually miss the old days, when Kiper would have players ranked pretty considerably different than would other analysts and the teams themselves.
I don't think Mel has become arrogant. He's a draft geek and a pretty nice guy. But he has become an "insider." Rather than follow his own instincts, I think now he bends much more to the conventional wisdom. Usually, by the time draft day rolls around, his board looks awfully similar to the boards from which the teams are working, it seems.
He wasn't nearly as accurate in predicting the draft during those early years, but he was challenging, and frequently he was right. He will still occasionally present a different, controversial opinion -- hyping Mike Williams, for instance (and obviously he was wrong) -- but in general, he seems to have become shaped to the needs of the Draft telecast. He doesn't seem to want to stray too far from conventional wisdom.
I still think that Kiper is a very good draft analyst. If you're going to point to his obvious mistakes, you must at least acknowledge that even the most astute teams make mistakes as well.
I don't think Kiper is as fresh, insightful and controversial as he was during what I think of as his glory days. I recall that Kiper was among the first to recognize the amount of talent Jimmy Johnson was assembling in Dallas during the early 90s.
Now Kiper is a good resource to learn during the weeks leading to the draft which players are "rising and falling." In reality, the movement probably isn't nearly as volatile as it seems. Analysts such as Kiper merely are beginning to discover what the teams are really thinking.
But it's fun, and it's entertaining. It's pro football for geeks like me when the news otherwise would be dead. For that, I appreciate the trail that Kiper helped to blaze.