Just tried the S3, must say it feels very nice in the hand, built felt top quality must say and is far from cheap plastic. It's still a bit behind the One X and 800 in terms of the texture but overall I was very impressed.
It is also not very glossy which was a big win and it felt so comfy in the hand even being a huge 4.8" the way it is designed it feels very much the perfect size. I tried to operate it in one hand and it wasn't to difficult. The front is covered mostly by the screen and I must say it really is an amazing screen. My gf owns a Nexus and even she couldn't get over the difference.
Performance wise the phone just fly's, it booted it from the battery being removed in maybe 20-25seconds, it was very fast and really caught me off guard. The phone was useable straight away, as soon as the boot screen was over you could get on with it, this could be due to the lack of apps/media/music but it was very fast. I tried my best to lag it down but I just couldn't do it.
Overall I'm very impressed with the phone, the OS feels pretty nice, it may not look as good as sense but it has so many usefully features that I can see people actual using. One thing that really giving me the upgrade itch is that screen, it will be a big step up from an s2/4s but other than that I think one could hold of pulling the gun.