Haswell demos at IDF last year were pretty awesome, so I think longer battery life at the same travel weight (and better overall performance) is pretty much a given.
If you don't use retina, you won't feel much of a difference, except in games (if you were playing games on an Intel integrated GPU before). Haswell has been generally overhyped. The improvements are relatively minor compared to IVB. CPU wise I think it's only 5-10% faster.
Haswell promises cheaper adequate performance, on less power. And speaking as someone with retinal (eyeball, not electronic) trouble, I'm really looking forward to a portable (i.e. 13") laptop with adequate performance that I can work on. (My 15" rMBP is great for work in the home office, but a bit heavy/bulky/expensive for carting around airports and foreign parts.)
(Don't expect to see a retina display on Macbook Air this year, though -- too power hungry. It'll probably just be a better 13" retina Probook for now.)
Completely agree -- I think there were early performance issues which were due to unoptimised drivers causing e.g. laggy Safari scrolling and that's caused a lot of misinformation to be out there. The truth is that, in practice, the IVB GPU has been more than fine for me unless I'm doing something that would require a dedicated GPU anyway.