i highly recommend the rb system as possibly the best value for money going around. the bellows focus is great for portraiture and the depth of field is very shallow rendering out of focus areas with great tones. the 140mm macro is a surprisingly good portrait lens and has some of the nicest bokeh of any lens i have used. i have a non-c 90mm that has quite low contrast for outdoor b/w but other than that it performs quite well. i personally see no reason why the newer, more expensive sd model would be better but at the end of the day, buy what you can afford and then buy all the film that you can't.

dane.