I've stopped using the Adobe Reader in favor of Foxit. Why? Because hyperlinks in Adobe Acrobat Reader launch Microsoft Internet Explorer regardless of your default browser settings. That's stupid. If I wanted to use MSIE I wouldn't have changed the settings and I wouldn't have installed Firefox.
Adobe made me angry... angry enough to actually look at what's in the Acrobat Reader directory. It handles FDF forms. Great, I've never actually seen one used. It has a QuickTime plugin. I have never once received or seen a PDF with a movie in it, nor have I ever met anyone who has. It has a WEBBUY API. I don't deal with DRM content, as I have Fair Use rights that are protected under international copyright law. I don't fart around with other peoples' rights, and I insist that they keep their fingers out of mine.
So I went looking for a replacement and found Foxit Reader. Foxit is under 2.5Mb in size and it requires no installation. It fits on my USB data thumb with my other utilties and must-haves. It does what I expect and only what I expect.
I don't do heavy PDF editing. Except out of curiosity I've never used any features of Acrobat except the PDF print driver, and that's now handled by CutePDF or direct export from OpenOffice.org. As a result I've never needed to upgrade from version 4.0. So the rest of Acrobat goes in the bit-bucket, too. If it turns out that I develop a need for a PDF editor you can bet that I'll consider the Foxit Editor first.