The fabric is slightly thinner and the cut is significantly tighter in the thighs.  I have 2 pairs of 559s I bought back in 2008, same size as the two new pairs I just received today from Levis dot com, and the older pairs are roomier in the thighs...with the new ones, I couldn't bend my knees comfortably.  So they're going back, will have to try the new 569s, which are supposedly "Relaxed Loose Jeans"...will keep my fingers crossed that they will not be of the opposite extreme!  Bummer...I guess this is the price of outsourcing production.

UPDATE 12/01/12: just got the 569s...problem solved!  These fit perfectly, like the OLD 559s used to fit.  My guess is that since Levis are now produced offshore, they downsized/slimmed-down all of their jeans so that they can be sold in the Asian market too instead of having to make two separate production lines.