Thanks for the link. I see that you lifted the earlier link on good faith from a presumably canonical source.
That is the link to show you which songs you have that are eligible to upgrade to iTunes Plus.
It does not convert your account to anything.
That may be so, but it is contrary to what iTunes actually said on the screen after I signed in. I don't recall the exact words but it was something close to "Your account has now been converted to iTunes Plus." It did not show a list of songs.
Now, when I click the link, I see the following text:
*iTunes Plus is the new standard on iTunes.*
You have successfully upgraded to iTunes Plus. Your items may still be downloading. YOu can manage individual items' progress via the Downloads link on the left-hand list in your iTunes application.
For more information about iTunes Plus, read our FAQs.
Operative word "YOU" have successfully upgraded". That, along with the previous message, suggests to me that my account is now permanently flipped. Maybe this is an inaccurate display message.
It launches iTunes and shows what is eligble to be upgraded. You need to log in (if you are not already) to indetify your account to the iTunes store.
When you upgrade your library (not convert your account), you have the option to keep the original files and put them on the desktop or delete them.
Nothing else happens to your account.
What do you think was converted?
Well, iTunes tells me one thing, and you tell me another. What do you think?