I haven't had much chance to push it to it's limits yet, but so far I'm extremely impressed. Gaming and app switching is so smooth and the OS level motion gestures make using the phone so fast and easy. I was disappointed when I couldn't run Dead Space, but that's due to EA not updating it, not the phone.
It also came with 50gb of Dropbox space which is a huge bonus. Wifi and Network speeds are stupidly fast for a mobile device where I managed to get upto 7mb download speeds while tethered. Also, with a ping of 121ms it's very easy to manage servers over ssh without a Wifi connection.
It does come bundled with some Samsung bloatware, but it stays out of the way nicely and never forces me to use it unlike HTC Sense in my 3 previous android phones. Coming from a HTC Desire, the size was a bit overwhelming at first but now it feels natural and comfy.
NFC is built in, but nowhere in England seems to really support it yet so I'm going to have to wait to try that out at a later date. The torch is very powerful and the camera is amazing quality and feature packed including 1080p video recording, smile detection and self portraits with the front facing camera.
Overall, it's an amazing device and if you're looking for a new phone then I would seriously recommend going for the Samsung S3.