Took the jump on my iPad Air. Here are my impressions:
New iOS 8 features - I really enjoy custom keyboards, widgets, and SMS relay. As an Android user also, they are something I am very used to and have wanted for a long time.
Jailbreak stability - TaiG 8.1.1 is just as stable as 7.1.2. I have had no crashes, resprings, etc. Obviously, YMMV.
iOS stability - iOS 8 is sort of frustrating. Many features, like SMS relay and call forwarding are a pain to set up because they either work the first time or don't. For me, I had to sign out all of my accounts multiple times, restart, and repeat until it finally worked. I still can't get instant hotspot to ever show up. Finally, the bug that really irritates me is how calendar events not from Google or iCloud are shown in GMT always and adding events adds them to the wrong time. It's a major error.
Other things - Since you don't have an Air 2, you don't have 2GB Ram so safari still struggles to keep tabs open and multitasking apps are cleared from memory just as much as 7.1.2. Battery life is still about the same. The wifi bug has not affected me, but YMMV.
Overall I'm happy with the upgrade.