I can play in all twelve keys if needed but I do use the Transposer for my editied SMF's and when I use a Style I re-write the song into a key thats comfortable for me. Rarely do I do original keys.
Many big name acts change the keys of their songs live to save their voices when doing many shows. What you can do at 10 PM at night, fully loose and warmed up in the studio is sometimes very hard to emulate live.
Not cheating if you can sing well but just don't have the natural voice to cover certain high parts.
As long as it comes out well no one cares.