I'm still waiting on mine to be shipped, but I've used the AT&T Note, the International Note, the AT&T S3, the Verizon s3 and multiple iPhones (3, 4, 4S & 5)
I'm trying to find a way to "curb" my addiction of swapping phones everytime a new one comes out. My main issue with my most recent phone (the Verizon S3) was the amount of bloat, the wifi in the notification, the fact that it still had not received jellybean, even though two other carriers had. I'm worried that the s3 will not receive an update after it receives JellyBean, at least on Verizon for sure.
I'm hoping that the answer to my phone addiction is to get as 'future-proof' as possible. Nexus is the equivalent of an iPhone when it comes to updates. It'll get those updates on the regular and with a quickness. Second, it has both a quad-core AND 2GB of RAM. Anything more than this is completely unnecessary at this point and probably at any point in the near future...
The thing with other phones is that these features (touchwiz, Sense, etc..) are automatically added to your phone with nothing you can do about it. On a Nexus, you're able to add features to your liking... your not stuck with anything extra you don't want or need.
Another thing about the S3 (and even the Note) is that actually using it as a phone sucks. It's not able to pick up signal in places that other phones have no issue and there's no 'negative space' on these Samsung phones. With a home button and capacitive buttons on the bottom bezel and almost an edge-to-edge screen, try to have someone else snap a picture for you or watch a video. Most people that I've ever had use my phone that don't have an S3 hit the back button when trying to take a picture, turn the screen off when trying to watch a video, etc... The Nexus has some room at the bottom, it's definitely more manageable than the Note.