I have this trim on my 'wish-list' as well.
I'd say Wild Blue hit the nail on the head: It's sporty due to its alu-inlays and pattern while still elegant due to its dark wood. It just matches the M-Line - especially when combined either with black leather or as a contrast, the all ivory.
Another advantage: It looks great combined with the B&W speaker colors. You have a great contrast which makes the covers in the doors pop out AND you have the alu in the trim match the covers, too.
Don't get me wrong, I still like the piano and the ash grain trims but I think they would be a better match on the luxury line edition.