w/Windows 7 x64/sp1
The .pdf and .rtf associations are set correctly to Adobe Reader and Wordpad but double-click or enter only responds by opening Windows Explorer. The right-click context menu lists "Open with Adobe Reader X" correctly and certainly works but is not how I'm used to working for the last however many years .pdf has been around.
I had hoped that if I could somehow get Adobe Reader into the Default Programs list and that that would help. However, Wordpad IS listed in my Default Programs and is set for .rtf and .docx but double-clicking .rtf does not respond by opening WordPad, only Windows Explorer.
HKEY_CLASSES_ROOT has Persistent Handler and ShellEx settings for .pdf but I don't know for sure if these are the relevant keys.
I'm also amazed (well, not really...) that MS apparently has no system for people to report bugs, only a system to take your money to (hopefully?) solve your problem...