With the exception of sniper rifles, nope. No iron sight at all. It simply zooms in towards the invisible cross hair.
And you know what? Gearbox said in their forum that its a FEATURE! Geez. Sigh. Their reasoning does little persuasion in convincing me that its a flawed design.
I finally tried the demo. Looks like it may be possible to play the game without digging in, and thus using iron sights only. One problem is, unless you're zoomed in, iron sights don't work like before, the crosshair is way to the left, so you can't really aim through the sights. Also zoomed in sights don't look realistic anymore, they don't drift at all, and recoil is very wimpy. Not sure about the sound, sounds much worse but I have a far inferior sound system connected to the 360, I just realized how much I need to upgrade. Also health is gone and checkpoints seem to be more frequent, other than that gameplay seems mostly in tact.