Are all the UIDs on a key supposed to be equal?

[Adam Funk]

Are all the user-ids (combinations of name, e-mail address and comment) 
equal, or can one be the "primary" one?

I started to generate a new key because the old has several obsolete 
e-mail addresses in the UIDs.  I gave my "main" e-mail address and 
comment in response to the "gpg --gen-key" prompts, then used "gpg 
--edit-key" to add UIDs.  When I then listed the key, they were out of 
order.  I had been under the impression (maybe it was just coincidence 
with my previous key) that the first UID is the main one.