I'm closing in on the end of this with 89% map cleared, a full party, and with what looks like only a couple of areas left to explore.
I have to say that, from the perspective of someone who has never played a Ys game before, I've really enjoyed it. The music is great, and combat really fast and snappy- I've never avoided a fight out of tedium, only because of the larger wandering monsters, which makes a pleasant change.
If I had one complaint, it's that there are lots of skills that are all very, very similar (launch-ups, knock-backs, stuns, area effects), and it would have been nice for Adol and Duren to have one skill that was a buff or something, rather than all of their abilties being variations on hitting enemies.
Boss fights are fun, I've enjoyed the focus on flash-dodge and flash-guard, the arena battles remind me slightly of Star Ocean IV at that point, but with more melee and less ranged combat. I managed to defeat the most recent boss I fought with the special move, which was pretty awesome as I managed to trigger it against his weak spot and it stripped off half of his second form's health!
Still, I've found the general sense of exploration and saturday-morning-cartoon friendly vibes in each town to be really refreshing. Can't wait to check out the rest of the series.