We play in Eb just to help the singer (and me when i sing), it's amazing how a semi-tone can make a lot of difference. For other songs that she or I struggle with due to the pitch, we just learn it in a different key. TBH, nobody notices and in some cases it sounds better than the original. For covers most punters wouldn't have a clue that you've changed the key. As long as you're all playing and signing in the same key then nobody really cares.