[Lalaith]

Lush, I too had always assumed that the 'slipping from his arms" line was significant and implied that a union had taken place - whether of body, or of spirit, or of both, however, was ambigious. I don't however think the fact that Beren was a man and not an elf necessarily makes the quote about elf marriage insignificant. There was also a 'moment of truth' between Aragorn and Arwen, on Cerin Amroth.
And I also agree that Tolkien was definitely an idealist when it came to male/female relations, but in a very non-condemnatory way. I think he had a very positive - if perhaps slightly unrealistic - view of women in general, compared to say, CS Lewis who was something of a misogynist. There are no purely evil females in Tolkien (except perhaps Ungoliant) The very few unsympathetic female characters - Lobelia Sackville Baggins springs to mind - have redeeming characteristics.