Lately I have been very into manual lenses as those who read this site before will know.
They are cheap(relatively) and build quality it top notch. And in many cases the image quality is not far behind the new lenses today. The one downside to using the different lenses with adapters is that everything is manual. But it does not have to be difficult! One of the reasons this is so easy and even fun on the Nex 6 (many other sony cameras have this and other camera producers have it too allegedly :), ..is due to the focus peaking feature. This takes much of the hassle out of focusing with the old manual lenses. Basically the camera will overlay a color where the camera have detected focus. Hopefully the video below gives and impression of how easy it can be.