Just upgraded my 590 to a 595 and it was all very straightforward.
Major changes are:
The inclusion of Spotify as an app (I use that a lot on long tours for music so most welcome)
The ability to push GPX routes direct to the unit from your phone
Adventurous routing to pick curvy routes rather than motorways
Some additional alerts for tight bends etc..
Anything else I've missed?
I followed the instructions HERE if you're feeling brave...
How do you push GPX routes from your phone?
I have a 595 and haven't found a way, so would you post up a guide of how to do it please?