I really don't see how a film can do justice to UBW. Besides the mish-mash of stories, one of the biggest problems with the FSN anime was that it had to rush through the "unimportant" scenes to fit everything into 24 episodes. Unfortunately, those unimportant scenes are actually very important indeed, since the player grows to feel a lot for the characters from going through the more mundane parts of the game such as cooking and washing up. It's the supposedly boring stuff that allows the player to relate to the characters and understand their personalities, and that differentiates (these) VNs from RPGs. They also provide comic relief, something which is always welcome 
Even though a film will only deal with one route, the short running time will force the producers to cull even more from the original game. The result may well be a perfectly good action movie, just as the anime was a perfectly good series (from what I've seen; I've only watched 2/3 of it), but it would be a miracle if they were to make something that did justice to the original.
Another fear of mine is that it will flood the franchise with a lot of new fans who don't really appreciate FSN, see it as just flashy swords and magic, and disparage the original (something similar happened with FF7 when AC and CC were released). Some will inevitably say that I'm being a big snob here, but meh.
