I don't understand what BSM is for. With your mirrors properly adjusted, there are no blind spots. I can watch a car move from my rear view mirror to the side view mirror, at no point are vehicles in adjacent lanes not visible in at least one mirror.
Here is an article about how BSMs are fixing a problem that doesn't exist:
http://www.autoblog.com/2009/08/20/do-costly-blind-spot-systems-actually-fix-a-problem-that-doesnt/
That article in turn links to a NYT article on how folks SHOULD adjust their mirrors:
http://wheels.blogs.nytimes.com/2009/08/18/are-blind-spots-a-myth/
This page has a nice diagram of how it works:
http://www.easysurf.cc/mirror1.htm
I'd rather spend a minute adjusting my mirrors properly than spend the money on the GT trim level plus the additional cost of BSM.
You know, I've seen people adjusting their side mirrors so they can look at themself seriously.....to make a hair do or some nose picking maybe, I've no clue why