I played with one today that one of friends was using on at&t...So were not talking demo, live model about 2 days old.
Ok it's plastic I know, but it does feel pretty solid in the hand. No creaks or anything like that, and it just feels right honestly. Very good dimensions all in all.
The screen is super amoled and over saturated but not to the point were your like omg this is blown way out of proportion. It's a very nice screen but a little colorful for my liking.
The camera was very good and the phone itself felt way faster then the demo I used the other day. The demo to me felt a little sloppy and sluggish...my friends was of course night and day compared to the demo.
Now would I trade my new HTC one in for the S4? Probably not, but I'm also a realist and have to honestly say it's a lot nicer then I previously thought.
Hope you new owners are enjoying it!