First of all, I would like to point out that while he did stick to his master formula for most of his beats since around 1995ish, there is an obvious difference between some of his old school ish and his newer formula. Clearly there is a difference between:
http://www.youtube.com/watch?v=Kh65Nmbrx4A
and
http://www.youtube.com/watch?v=nSh1dLlBaHw
So its not exactly true to say all his beats sound exactly the same.
Second of all, repetitive from what I've heard means two things in this section, so I'll break down why both of them are weak criticism's of Dj Premier.
The first way in which I hear people use the term "repetitive" when refering to Premier is "all his beats sound the same." Which means you are basically criticizing him for having a signature style. My question then is this: When did that become a bad thing? His style is the best, that's why he continues to use it. It's called being consistent. I'd rather he stick to what he does best and do that to perfection then try to dabble in other styles and have it come out half @ssed. Also, I think it warrants mentioning that other great producers have signature styles too. They may deviate from them a little more than Premo, but that minor deviation does not warrant overlooking the far superior quality of Dj Premier's catalogue.
The other way in which I hear people use the term "repetitive" is an even weaker criticism than the signature style argument. Basically the second repetitive argument is "his beats just loop the same 5 seconds or so over and over for the entire beat." Newsflash MOST HIP HOP BEATS DO THIS! That's why its called a beat. A beat is supposed to be a few seconds of music looped over and over. That's the foundation of production. Pete Rock does the same thing, RZA does the same thing, everyone does that. What do you expect there to be a guitar solo in the middle of the beat? Give me a break. The same people who criticize beats for not being complex are the same people who count up syllables to determine how good a verse was. It's not a legitimate criticism.
Furthermore this is all besides the point. Bottom line, his beats sound the best. People used to put him at number one on their GOAT lists for exactly that reason. Now people have gotten so caught up in trivial technicalities that they are just trying to find any BS excuse to discredit the legend. You aren't supposed to be breaking down these beats like that. Just nod your head and enjoy the beat. Beats are for enjoyment. And I think its funny how everyone is preaching this anti-elitist gospel and making a big deal about how its more important that the music be entertaining than that it be technical, but then these same people turn around and criticize Premo for not being technical. Dj Premier is an entertainer. His beats are the most enjoyable to listen to. That is why he is number one.
Not to mention the obvious. He uses different samples in every song, different drums (he may have recycled drums a few times without me noticing, but I know he has a sh*tload of different drum patterns because I've sampled them out of his songs on FL Studio), and different scratches/samples of MC's in his scratched choruses. That's enough variation to keep me interested.