Ok,so I just came from the Apple store after trying some hands-on with the iPadAir 2. The vibration from playing music is BAD. I tried it with both EQ off and "Bass reducer" EQ setting, with volume at 50%.
As soon as I got home I did the same with my iPad Air. Removed the Smart Cover and did the same thing. No comparison. The iPad Air 2 vibrates pretty badly, particularly about an inch and a half from the bottom, and resonates throughout.
Now, I don't regularly use my Air as a music player, but watching web content with sound - it would really bother me.
IMHO they've gone too thin.
It comes down to a simple choice for me: endure Safari tab reloading on my iPad Air
Or
Endure excessive vibration from sounds emanating from the iPad Air 2.
(Typed with my iPad Air)
I don't think that will matter. I tried three display models in the store. They ALL vibrated badly. BADLY.