Personally, I don't think this love story is even strong. The only good point coming from this little 'arc' as I'd like to call it in Adventure Time is that we are dealing with character development from FP's side of the story, but not on this couple's relationship. Even in the debut of this couple I wasn't convinced, because all Finn was doing was giving in to his temptations (sorry, I don't have a better word to describe my idea, but I hope you readers do) and FP being a curious child and all. Until I see real romantic development in this couple, I don't think it is that great. And don't give me bullshit about the show being insane, the creators of the show have some knowledge of what love is.
Not true love my friend, just an infatuation. True love would truly mean that through crap and diamonds will the relationship strive. Now, the best the couple has gone through is water (no play on words intended), as they only have minor problems with FP's flame body and having that one scene where the two went adventuring. Again, maybe I might have missed something, but I really cannot see any strong 'I just fucked up and I need to find a way to make things up for [insert boyfriend's/girlfriend's name]' scene yet.