I use the app on windows phone and while the quality of the app itself is fantastic, the translation is often frustrating because you're given only a single choice of words. I often type a word or phrase and get as output something that I know is wrong, but unlike google translate, since there is only a single result, I can't click on words of the translation to see the other possibilities that might make more sense.
This is THE major issue that needs to be fixed imo. I can't imagine the bing translator team isn't aware of it, but at the same time it's really puzzling to me that it's not already a feature. It seems so basic... Most words have alternate meanings and therefore multiple translations and too often we get output that just makes no sense and the only way to get the correct word is to go to google translate.
The voice translation and camera parts of the app are excellent though. If the above was fixed it would be the go to translation service for a lot more people but sadly even though I'm on WP, I still have to use google's mobile site a lot of the time. :(
