The Timbuk2 sleeve is a very decent option if you want to protect your Kindle Fire, but use it "naked." Unlike a case which might offer a hands-free stand option, the sleeve only protects your device when you're not using the tablet.
The bumf states quite categorically that this sleeve "will only fit Kindle Fire." It may or may not fit the Kindle Fire HD (I don't know), but I can tell you for sure that you can fit a Google Nexus 7 or Kindle Keyboard (aka Kindle 3) comfortably in it.
The padding is certainly a little tough, but that's a good thing. If you think not, you may as well just use a Jiffy bag to protect your device.
The sleeve is perfectly fine, but I'm not sure that it's worth the asking price. At the time of writing, it's 25% the price of a Kindle Fire. Not easy to justify that, but if you're after a sleeve, this is one for the shortlist.