Totally with carnage matey, used Carmen at LGW, it was actually OK, as it was an improvement over the previous take what your given school of rostering. But i did work pretty hard at bidding and when it went wrong it went spectacularly wrong for me. On that fleet i was pretty senior but i'm way more satisfied with the Bidline system even in the bottom 20 of a 580 FO fleet.
I have to be careful what i bid for and it takes an hour or so a month and worst case is i get a blind line with a preferencing system. Which is all i had at LGW!