Personally, as a small LL owner, my take:
index page = 'enter' solely used as entrance to the freesite
internal pages, enter is ok as long as it isn't blind, so 'Enter here for anal movies' is a no go, unless the sponsor site is called Anal Movies.
As a submitter, I use 'enter' only on the index page as per usual, but lately have been using 'Enter Paysite Name' as a link on internal pages. I don't see anything wrong with that
