Kindle Gets Smart on PDF and EPUB?

I was very surprised to read today that the Kindle was now able to read PDF and EPUB files. Wow. There's one big catch--it's not Amazon that has set up this capability. A developer, who swears he didn't hack the Kindle (though I have my doubts), came up with the application that allows the formerly unavailable formats to be viewed on the Kindle. But as with any hack, buyer beware...