If you actually read the specs, thunderbolt 2, faster SSD, and intel 6000 graphics are fairly substantial additions.
Depends on what you do with your computer.
ThunderBolt 2--I don't think I know anybody with even a single TB device, much less a TB 2 device. So I would expect this is a pretty irrelevant difference to most people.
Faster SSD--it's only faster in terms of sustained throughput, which most people won't even notice. How often are you waiting on your computer to read/write gigabytes of data to the internal drive? (Because as soon as an external drive is involved, that will be the limiting factor in terms of read/write speed.)
Intel HD 6000 graphics--only relevant if you play modern, intensive 3-D games. And if you do that, you're probably not using a MacBook Air to do it.