I had the 3 and sold it to get the Air. One of the big reasons was to get all my devices up to lightning adapter which is super convenient.
I like the Air a lot better. I Don't really notice the performance difference as much as the weight and feel. It's an incredible difference!
That said, I wouldn't buy an Air now, You've waited this long, might as well stick it out till the next gen goes on sale.
I sold my 32 gb 3rd gen for like $375 then got a 16gb Air for $500 w/a $100 Target gift card on Black Friday so it only cost me $25+ tax to upgrade.