I would urge everyone on Air 1 to sell it immediately. Take a few hundred dollars hit but buy Air 2 and then keep it for 2-3 years.
I sold my Air 1 and got 2 Air 2s. 2GB RAM and 2.5 times faster GPU is a REAL upgrade of all time.
It'll be worth it when you see real differences in third party apps. Right now a second or two (if you're lucky) quicker loading times is the main difference.
For now, and of course this will change, the Air 1 and Air 2 run every graphically intense app identically. I know exactly what will happen in June when I get my Air 2 on my annual upgrade ... I'll be sitting there asking, "This is it"? Hopefully by then something is on the App Store that truly shows the difference but I'm skeptical. The iPad 4th gen still runs most graphically intense apps at near identical performance to the iPad Air. Games that use Metal, like Asphalt 8, look stunning on the Air and Air 2 and run at identical frame rates with all effects enabled.
The Air 2 has legs, and it will stretch them eventually, but right now anyone insisting there is an instant and immediately perceivable difference or "wow" factor in terms of performance is bending the truth.
The annual cycle means that NO iPad since (in my eyes) the iPad 4th gen has been given time to be pushed to what it's capable of and it's certainly never shown its full hand within 12 months. These devices are so powerful that developers are still getting plenty out of the outgoing model then a new one comes out. This means they will never fully utilise their power in a mere 12 months.
What excites me more is what the iPad Air 2 will be doing this time next year, if not sooner. However by then the Air 3 will be out and the same people will be logging on here, waxing lyrically about the Air 3 specs, calling the Air 2 "obsolete" and "old tech" and running it down.
Happens every year on here. And I GUARANTEE that more than half of those over the various threads on here who are going on and on about the Air 2's potential longevity won't even keep their Air 2 next year anyway!
I've a cheek to talk though, I upgrade annually (company provide me with a new iPad, the amount is discounted 20% and the remaining balance is deducted from my salary before tax over 12 months) but it's always in June meaning I'm near the end of the iPad's "life" when I get the latest one. So for me this iPad Air is "only" 6 months old and it screams (well, as long as it's kept on 7.1.2).