Millennium sank 10 of those 16 inches in its first two years (by 2010), so the rate appears to be slowing (if it is still sinking at all). There has been no assertion the building's seismic systems are compromised in any way.
I don't know how common the lean is for newer towers, but I can say with certainty one of the old buildings I see from my office, the gorgeous 1892 Burnham and Root-designed Mills Building at Montgomery and Bush, is leaning substantially. Because of how the streetwall of towers is lined up along Bush, this building's lean is immediately obvious to the naked eye from my office window--several inches out over Bush Street (not detectable in this photo, which is not mine)
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