I've been listening to Wilco's forthcoming Sky Blue Sky, and Nels Cline, the band's new guitarist, is a revelation. Elegant and forceful, he helps take Jeff Tweedy's songs into uncharted waters. When was the last time such a prominent band, at its peak, added a new member who made such a noticeable impact on its sound? I'm sure there's a precedent, but I'm not coming up with it (and before you answer that Johnny Marr is presently having such an effect on Modest Mouse, recognize two things: (1) I think his impact on MM is considerably more subtle, and (2) I don't think the Mouse is in Wilco's class, no matter what the SoundScan numbers say).
And I'll go on record: Sky Blue Sky is an unspeakably brilliant album, maybe the best thing they've ever done. It comes out on May 15, and you should own it.