Don't have any pictures to add to the thread that will beat the previous poster's excellent pics. But my initial thoughts are very very positive. I love it.
yes, it adds thickness. It's kind of a lot. But I LIKE it. Not that the iPhone 4 was too thin, but, this gives it some weight, bulk, and just an overall nice feel. It's not like Otterbox bulky. It's nice. It's hard to explain, but if you are even the least bit concerned about adding height to the phone, don't get this.
The soft touch feel on the back is nice. It isn't as soft as the Incase Slider (I own one for the iP4) but that's a good thing because my Incase scratched up and I don't think this one will as easily.
The "amplifying" of the audio is pretty good. I noticed in my apartment elevator my ringtone was much louder than it normally sounded. It's hard to explain - it isn't MUCH louder, but it's noticeable enough that you know. It isn't muffled. Wouldn't call it acoustic either. It's just...different. But a good different.
The form factor on this case is better than I've seen on any of the other battery pack cases out there so far, so if you're considering this or exogear, mili, etc. I'd definitely go with this. I'm loving it.
Only thing I can't figure out (reading the manual that came with it) is if it's best to let the phone drain down to 10-20% and then use the pack and charge it up as far as possible, or if it's best to charge the case up and then turn it on and let it run in place of the Iphone battery for X amount of hours and then let the iPhone do it's thing once the battery pack is depleted. The website and manual both say different things. Hmm.
But overall, very good quality. The flash also doesn't distort at all from what I've seen. I took it in an entirely dark room. Even the Incase Slider's "flash ring" showed signs of flash distortion on certain parts of the images. I can't notice a difference in this. Probably because when you see the cutout, it's almost like it gradually increases as it goes outwards, it's hard to explain without seeing it first hand. If anyone with a good camera could take a picture it'd probably help. But mine is great on the flash.