I picked up mine three days ago. It has 16GB of internal storage and a microSD slot. I transferred to this from a Dell Streak 5 which is over two years old. The difference is night and day. The Butterfly is incredibly thin and light, and even when I put a protective case on, it didn't actually get any bigger (so it seemed).
Since my Streak was in an Otterbox case with a double layer, making it significantly more bulky than the phone's actual dimensions, the difference between the dimensions of the two phones is even more apparent. Here's a comparison of dimensions and weight; the height, width, and weight are significantly different.
* H: 152.9 mm
* W: 79.1 mm
* D: 9.98 mm
* Weight: 220g
* H: 143 mm
* W: 71 mm
* D: 9.1 mm
* Weight: 140g
Everything is blindingly fast, and GPS location is hardly takes a second. I am not used to Google Maps responding nearly instantly. I have to say the screen on this phone is incredible. Not only is the full HD 1920x1080 resolution stunning, the colour saturation and brightness are amazing. Ok, LCD3 isn't AMOLED, but I'm perfectly satisfied.
Coming from the Dell, and having two spare batteries (one of them a monster 4800mAh Mugen), I was concerned about the battery life of a phone with a non-removable internal battery. I should not have been concerned. I installed the Go Power Master app, tweaked a few settings, and created a power-sipping profile which is challenging the battery life of my Dell. This is what the power status looked like last night.
I left it overnight without charging it, and right now it's at 26% after 32 hours. Impressive. I'm going to tweak the power settings a little further, charge it up again, and see just how much I can squeeze out of it.
I can't say enough about the screen and image quality. It's odd to say, but whereas images on my Dell looked like they were well beneath the screen, images on the Butterfly are so vivid and sharp they look like they are sitting on top of the screen. Here are some screenshots (taken using the phone's screen capture function), of my photos displayed on the phone itself. Needless to say, these photos were taken with my Nikon DSLRs, not with the phone camera.