Hmm... so according to the article, the only way to have an application seen in LaunchPad (short of an AppStore purchase) is to move it to the /Applications directory at the top level, since it knows nothing of sub-directories. Wow, I expected something less kludgy from Apple, specially given that many widely sold applications (MS Office, Adobe etc) routinely install software in locations other than the top level /Applications directory.
That still doesn't explain the weirdness with iWork. I can see it's sitting inside a sub-directory under /Applications/iWork '09/. I installed it through the DVD I got, not through AppStore, ergo, LaunchPad should not pick it up. Still, it shows up in LaunchPad. Uh...?