I don't really agree that you have to have finished Torchwood to watch Utopia, I mean yeah it takes place after Torchwood ends technically however there really aren't any spoilers that I can think would ruin Torchwood and it explains a lot. But if you want to go in order start with Empty Child then through end of S1 DW then Torchwood then Utopia and the next 2 DW.

I read somewhere that they were going to show Jacks bum in Bad Wolf but they decided to edit it out to keep it family friendly and that John Barrowman was offended because he thinks he has a nice bum (and yes he does)