Really? I've never felt it get hot. It feels lighter than my iPad2 (although it may be heavier -- but I really don't think so). The UX is almost strictly worse than the iPad2, but at less than 50% the price, its a better deal (given they both have serious deficiencies today -- but $199 for a seriously deficient device feels much better than $499).
Web browsing kind of sucks. Like the YouTube experience is crazy buggy.
I find the keyboard hard to use for anything, but the smallest notes.
Getting content on the device, e.g., movies I've transcoded, is an exercise in pulling out my hair. Tedious and time consuming.
And this is just me doing stuff on it that people say I should be able to do well on the device. I don't even include the deficiencies for things everyone knows that it doesn't do well -- so it gets a free pass on it.
That said, a Kindle 3 is only 250g and an iPad is 600g which is what the comparison is in my mind. I am not sure where the ~400g Fire lies in that regard.