But, once again, no one else has taken on Ian's proposed task of contributing to the list, which, again, is more interesting to me than quibbling over opinions on individual works. So, qt, your contribution?
What's the point of contributing lists if we're not going to discuss their content? After all, "opinions" are what this is all about in the first place. But I suppose we could bring a few more into play first.
The trouble is, I find it very hard to name important works since 2000, as a lot of the composers whose work has meant the most to me in the past (Lachenmann, Ferneyhough, Dillon, to name but three) have not quite delivered in the last few years, in my opinion. Perhaps I should make a small negative list, a list of important "let-downs", to illustrate my point.
Lachenmann: stagnation since the opera, broken only by the 3rd quartet. I completely disagree with the praise for Concertini, as it's really just the work of a seasoned craftsman showing his chops - Schönberg referred to his Theme and Variations op. 43 (I think), which has one version for full orchestra and one for wind orchestra as "one of those pieces one writes to enjoy one's own virtuosity". That's the impression Concertini made on me, and Helmut pretty much admits it himself.
Ferneyhough: his big, important piece, Shadowtime, disappointed me. The vocal writing has taken on a sort of camp flippance, and a lot of the instrumental writing seems interchangeable in a way that wasn't the case up to the mid-90s. I was listening to the Etcetera CD with La Chute d'Icare and some of the Carceri pieces the other week, and was struck by how superior those works (more the latter) are to his recent pieces. I popped over to Witten last year just to hear his new string quartet, and while it did intrigue me, it also left me unsatisfied. To my ears, his recent pieces display a bizarre combination of cruder gesturality and more academic structural working, leading to something that lacks the potency of 80s and 90s pieces. Listening to the Etudes Transcendantales, for example, every note, every nuance seemed meaningful. Listening to Flurries or The Doctrine of Similarity, however, I felt that he had generated a pile of material without really shaping it, without creating contexts. Perhaps that has something to do with the more significant function of the computer in his composing?
But to salvage some "positive" things from the last years, let me add Lachenmann's 3rd quartet, "Grido", to the list, something by Giorgio Netti - maybe actually that mammoth saxophone piece Richard finds so dreary, even though I find its length extremely problematic myself, or perhaps the less contentious string quartet. With Furrer, Fama certainly marks a stylistic turning point, and I'd agree that it's an important piece, though my feelings about it are somewhat mixed. How about Finnissy's History of Photography in Sound? Spahlinger's piano septet Farben der Frühe also comes to mind, though I should give that another few listens before I say any more about it.
EDIT: I forgot to mention Mark André, who's really been coming into his own this millenium. One fine recent piece is ...durch... for sax, piano and percussion.
EDIT 2: The late Mark Osborn (d. 2002) - I consider his orchestral piece Vinculum Substantiale (2000) a major achievement.