I have an older Sony MZ-R30 md recorder/player. It works great, but watch out for these flaws possibly also in newer models
1) the control buttons are very small and fragile, can become internally misaligned with the internal switches.
2) the small input/output jacks can introduce noise and static if not cleaned and handled carefully.
3) some of the control/programming sequences are very awkward to execute.
4) the unit is subject to microphonics (phisical noise) when recording or playing back.

Also check out the built-in copyright protection features, which in some older machines will prevent you from making multiple digital copies even of you own originial material.

On the plus side, the editing capabilities of the larger (non portable) machines can be awesome. Dance music can be programmed to repeat so seamlessly that dancers don't even notice what's hapenning. They are also great for theater, sound effects, etc.
MD