Let's face it, they're all pretty much uneven. But come to think of it, the Boulez cycle strikes me as one of the more "even handed" ones. For me, his "DLvdE" is the low point. The high water marks, for me, would be his Vienna M3 (get the sacd hybrid version); the M6 (the first item in the cycle), and the three shorter song cycles disc (with three different singers) . The two Cleveland items (M4 & M7) are pretty good too. The Chicago M1 is quite good, although the scherzo is a tad too fast for my liking. The Chicago M9 has a very good first movement, but the last three movements are a tad prosaic (and swift in the last movement). I like the Berlin 8th, which was recorded in the generous acoustics of the Jesus Christus Kirche, although the end of Part II turns out to be less thrilling than his ending to Part I. I'm not wild about the Vienna M2, but the DVD of M2 from Berlin's Philharmonie addresses pretty much all of the shortcomings of the studio recording (little or no organ being the biggest shortcoming).
Anyway, this cycle is easily good enough that I hope DG is going to throw it into some kind of nice box (with ALL of the items inclduded, please). I see that according to HMV Japan, DG is coming out with a Boulez Bartok box (yeaaaaah!).