I've tried the exact same things.....deleted the ipod photo cache, restored the iphone, rebuilt the iphoto library, created a new iphoto library, reinstall iTunes, confirmed I'm not running out of space, etc. And all of my photos are still not syncing. Photos that I take w/ the 4s camera don't end up in the photo library and photos that I've taken with my DSLR don't end up there either. After syncing completes and I go to the photos app on the iPhone, the spinning wheel at the bottom spins indefinitely. It's driving me nuts.
I was on the phone with AppleCare for 2 hrs the other day and they couldn't figure it out. I've gotta believe it's a software issue and that a fix will be coming shortly.....or maybe I'm just optimistic? One of the main reasons I purchased the iPhone was because of the camera and photo capabilities.
I've got a 20' iMac (2.66 ghz Intel Core 2 Duo) w/ 4 gb ram running OS X 10.7.2 Lion. All Mac all the way and this is the first time I have to disagree with "it just works".