I had a Kindle Fire and liked it but I liked my old kindle first edition with the ink screen because you could very easily read outside or at the beach. I just bought a Nexus 7 and I like that for browsing the web and doing all my reading except for outside. If I want to read outside I load up my first kindle and take it with me. The Swype function on the keyboard is also great on the Nexus 7, I’m not sure if the newer Kindle Fires come with it.
I have not bought the Kindle Fire, but my son purchased a Nexus as soon as it came out. I have taken it over. Just upstairs in my bedroom. I had been using a tv up there and a bluray system that let me stream netflix. After getting the Nexus up there, I can surf the web, watch Netflix, and have found I am not turning on the tv. And for reading I still have my Kindle 3G. For real computing, I still sit down at my desktop computer. I have it setup to work like a laptop, though, or better, with wireless keyboard & mouse. But for crunching power, nothing beats desktops, still.
I believe the Kindle Fire is comparable in apps to the Nexus, and a bit cheaper.