sorry, old thread, but I am wondering the same thing. I have a 2011 model and I would like to know if I would gain anything by trading up for the newest model. weight savings? compliance? simplicity? i don't have any plans to put rim brakes or a rear rack on it.
I had a 2011 I bought off ebay (large) that ended up being just a tad too large for me, so I got a 2012 medium that has been a dream. I don't notice much difference in the frame itself but the new fork feels much better when it comes to compliance.
Not sure you'd lose much weight other than what you'd lose by hacking off the vbrake bosses (I suspect that is 3-4 oz), though its probably thinner tubing that made the fork more compliant so there could be some weight savings there as well. I still have the 2011 fork, and I think its a similar steerer length to my 2012. A new fork will be here in a couple months, once the 2012 is off I will try and remember to ask shop to weigh both of them.
I *DO* like the look without the vbrake bosses. Pretty sure its not actually simpler, but it looks simpler and there is a few less protrusions to collect mud and grass.
IMO you don't need to upgrade. I've ridden 2005-2006, 2011 and 2012 monkeys and the biggest upgrades were the tweak to the caliper mounts that made it easier to remove rear wheel (2010 or 2011) followed by the steeper top tube (2011). The fork change in 2012 was nice also but if you were looking to upgrade the fork there are still probably better options for a rigid fork around the same price (cromoto comes immediately to mind).