First thing you'll notice when you pick it up is that it's incredibly solid. It's got hard aluminium edges and a rubberised back that feels soft and grippy. It easily fits in a jacket pocket, and just barely squeezes into my jeans pocket (although I wouldn't recommend doing that). It has a front-facing camera, but no rear camera, which is fine because you shouldn't be taking photos with a tablet anyway. There's also the usual volume up/down rocker, power button, microUSB and headphone jack. Sadly, there's no expandable storage, but Google is emphasising its cloud portfolio, so it makes sense.
The boot time is very quick. The screen is bright and vivid at first glance. Then you start scrolling around the operating system and it's perfectly smooth. Google used the word "butter", and so far, that's proving to be an apt description.
Jelly Bean is lovely, and it really utilises the tablet-sized screen much better. For example, there are six shortcuts (plus the app drawer) in the home row.
We'll need to spend more time with the Nexus 7 before we do a full review, but my snap judgment is that there is no reason to buy a Kindle Fire over this. It's brighter, sharper, faster and infinitely more capable. Your move, Amazon.