There's also the tragic lack of an antiglare option (rather, the mandatory presence of a glare-inducing piece) on the mba vs. mbp15hd/mbp17.
I wish they'd fix that for the ACD 27 and iMac, too. I've been using Dell U-series IPS panels (U2410, U2711, U3011) for everything due to being matte and cheap ($400, 750, 1k!), but the new Apple display with the docking is pretty awesome, so I ordered one. Sadly, the glossiness means never using it in a room with external lighting :(
I'd go with a MBP15HD as my only laptop, but instead I do mba13 + mbp17.