Oh God, I love this unit!!
OK, I got it some time back, so by now it has probably been superceeded several times. That doesn't mean that it is out of date though; oh no! The 520 does everything I want it to and more.
The controls/menu system are intuitive and easy to use (only had to get the handbook out a couple of times!).
All the MD functions are available: erase; move; split; join etc.
The sound quality is, of course, quite superb and cannot be faulted - in my humble opinion. There is an optical output on the back which I haven't had the chance to try, but I am using the digital co-ax link from the CD player and that works very well.
My only dislike is the keyboard on the remote control. Being used to a qwerty keyboard, as most of us are nowadays, I find it difficult to use the abc keyboard as laid out on the remote, when entering track info. Sony do a qwerty keyboard that can be attached, but I don't want to lay out extra cash just because I find something "a bit fiddly"!

Not sure of the current retail price - I paid 200 sovs.

Overall, a smashing unit which I recommend wholeheartedly.