the r-50 is OLD SCHOOL. It is the 3rd generation sony deck. They are built like a tank, unlike the new ones. The external battery compartment is a big plus, but most new ones have it.
The drawbacks are you can't change levels while recording and no mdlp support.
If you can get one in good shape, it should last you a while. Mine has seen lots of action and still works great.
JAson