Haven't spent a lot of time with this, as the Fire I bought was actually for my step-father, but I wanted to make a few comments having used one.
1. It's the right size
The iPad may have pioneered the ten inch tablet, but the fact is the form factor is just too large to qualify as easily portable. 7" is a decent size, it'll fit in a larger pocket, although you're pushing it if you do that, but it's big enough (and high resolution enough) to show a web page with very little difference between it and the desktop rendition. The Fire is the size of a paperback book. The iPad (and my Lenovo K1) is the size of large pad of paper. No contest, the Fire wins here.
The fact the screen was large enough actually surprised me somewhat. The first site I visited was Amazon.com, and it looked perfect. No sign of scaling or anything that would make it unusable. Of course, I have pretty good eyesight, so it's possible that someone with poorer eyesight may need to zoom the screen a little.
2. Web browser felt slow
Amazon has been promoting the browser technology they're using, whereby significant amounts of each site are rendered by their servers. The result seemed to be heavy latency, whereby the page itself might appear in a flash, but the flash occurred quite a few seconds after the request. Supposedly you can turn this off, so this fact is more of a "This isn't a feature" than a "The device is flawed" type criticism.
3. Standard ports
USB charging, with a regular micro-USB port. Yay! Should I be happy about this, or just expect it? Well, the K1 experience hasn't enamoured me to proprietary connectors.
4. The keyboard: not as bad as claimed
I had no problems whatsoever setting up my step father to access my wireless network, which required the usual password entry etc. There's been criticisms that the keyboard is too pokey and prone to fat finger problems. I didn't come across any - and I was using the device in portrait mode.
5. Very easy to use and clean
I was fairly impressed with the user interface. Looked nice right out of the box and everything was easy to find.
There are a couple of features missing from the Fire that prevent it from being a full tablet, but it's a really nice media device and it might push tablet makers to make something around the same price point with the same form factor.
Professionally, I need to be familiar with tablets. The experience of the Fire means I have some idea of what I'd buy for my own use. Nice work Amazon.