v2 adopts many of the same stylistic cues as the original and most importantly has the exact same bendy, flexible sole. it does introduce a new padded tongue which is nice in theory, but it protrudes a shade higher up on the ankle as the original did. i'm actually tempted to cut off the extension just to keep it more comfortable and rounded at the top of my foot. v2 also has a reinforced toe for added protection. otherwise, it's the same feathery and whisper quiet shoe that weighs in at 7.2 ounces (the original came in at i think 6.9) for my size 10s.
the goal of the 3.0 is to promote a better (or mid-foot) heel strike in order to prevent the leg from taking a pounding of the joints. nike originally doled out three separate entries for the free - the 7.0 (closest to a shoe), the 5.0 (middle of the road) and the 3.0 (closest to barefoot) for an easy to use progression towards the end goal. back in 2005, i bypassed the 7.0 and went straight for the 5.0, which gave me a good re-introduction on how to run. i picked up the 3.0s in 2007 and have never looked back.
i still prefer the aesthetic of the first - it's a cleaner look, smaller swoosh, muted colors - but since it's nowhere to be found, and i found v2 for such a deal, i had to pull the trigger before they became obsolete. i can't fathom the thought of running in anything else!