The Skopar lenses are small, light and handle very well on the Nex system. One tip, don't go below 35mm on the Nex-7 unless you're using SLR lenses. Problems with colour shifts doesn't happen with those lenses. Nowadays, I'll only use the longer focal length lenses on the Nex-7 because of this issue of having purple edges to the image. It is correctable in post but I really don't want to go and make even more work for myself.
I can recommend the Voigtländer Skopar 50 f2.5 as it has a lovely signature and the images come very close to the Leica look many people are looking for.