If you own an SB130LR, SB150, or SB165, I would personally not upgrade unless you really have too much money
There are some nice refinements (cable management, threaded BB, UDH derailleur) on the new line up but unless you MUST have the SRAM Transmision drivetrain and need the UDH derailleur standard, I dought that anyone would notice real-life differences between the SB137 (ie SB130LR) and the SB140 29er, the SB150, and SB160 (just change the airshaft on your fork and stick an offset bushing on the shock and the SB165 is unchanged.
For those who have an SB110 or SB115 and are not Lycra fans but like a fast, capable, and fun trail bike with massive "down country" capabilities, the SB120 upgrade might be worse it.
And this is coming from someone that pays his bills from selling Yeti bikes.
Then again... I might, possibly, maybe, perhaps, be completely wrong ;)