ICS is optimized for dual core. Quad core is just overkill at this point as the software needs to catch up.
edit: Just realized who the OP is. Guess you're still not happy with your Nexus
I wouldn't mind quad-core if the rumors of it being better on battery(more optimized with 4G chips) are true. I don't need extra processing speed if my phone is going to last an hour.It has nothing to do with me having problems with my nexus.
For me have a quad core CPU in my phone is a mark of a new era if you may,it represents a new generation on power on your cell.
The 4s is not 4G.. lol, so I hope that was sarcasm. As much as I do not like Apple, I still keep up with the competition. The iOS 5.1 update did not magically turn your phone into a 4G device(some of my friends thought this too). 4th Generation, yes.
And no, the only NON-Nexus I'd maybe consider would be the Galaxy SIII.