Finally a topic about this.
My dad got an MBA 11" 128GB/2GB on Thursday here in the Netherlands.
And the first time and couple of times after it booted in 15 sec.
But when he installed the update to iTunes is began booting in 25 to 35 sec.
i Tried the usual suspects as repairing permissions and even disabling spotlight.
But no go still booting in 35 sec.
So what i did was a clean reinstall from de USB stick and although that saved me 1.2GB of space (left out the other languages) it never booted in 15 seconds.
Hopefully my own ordered Air 13" 128GB/4GB will arrive this upcoming week, so i can see what mine does with these times.
I personally hope that there is a setting or something that i'm missing to get it back at 15 sec. Although it looks like some strange thing apple did to it