I too am looking into a 525 dual sport. I know of a few locally and they all seem to be doing well. I did post a question in the thumper forum about valve train reliability. It seems there is a fix for the older bikes and I assume the newer ones are good to go right outa the box.
I have ridden the 520 on the street and it does quite well. However the revs seem a little high for fast roads. I know the bike will top 100MPH in stock form, yet the gearing is still not ideal for the street.
I can think of no other bike more worthy of dual sport conversion.
Chris