Yeah, I wouldn't switch from the S3 or the Nexus 4, but if I were buying a phone now or switching from anything pre-S3, just nothing beats this. Every single feature is hands down the best on the market.
Sure, the design could be better, at least it's better than the S3 because of smaller bezels though. At first I was disappointed by no design change (because I thought the S3 looked bad), but everything that came after that was just perfection.
I think the S3 was more solid than the Nexus. Perhaps the Nexus can feel/look more solid, I guess. It's hit or miss because I know people who dropped it and it survived and I know people who just accidentally hit something with it and it was ruined.
With the S3 I've only heard of one story of broken back cover. I have a friend who drops hers at least once a week and it only looks a little scratched.
I guess Samsung's choice of materials is basically functionality above looks. HTC phones use metal unibodies, they look solid but have to be serviced more often. They are heavier and take more internal damage on impact because of hard covers.
Samsung's plastic is more flexible and has smartly engineered impact zones. Sony Xperia Z is drop-resistant barely because of well engineered impact zones, cover design and flexible plastic.