I bought the NEX5 with the 16mm lens that I use for for snaps at parties. I have an M adapter as well as an F-mount adapter that allows use of G lenses (yes, I can control the aperture of the lens via the adapter).
While being able to use my M mount lenses (21,35,50,75) are great, using the NEX5 with F adapter is especially fun with zoom lenses.