Because of the problems with dust spots. we've been seeing if the M9 works for us using only one lens. It does turn it into an extremely expensive single lens compact, but the dust spots are proving so time consuming to remove.
My personal favourite is the 50mm f2 Planar. I tried taking this single lens outfit out yesterday to see if I felt restricted by it.
The simple answer was no. Actually it was very liberating and I enjoyed the simplicity.
Multi Image Panoramic Stitch.
Words and Images - A