I've got just over 50% map completion now. This game is fuuuuuun. Totally recommend Celceta Sea of Trees to Ys fans - especially those who liked seven. The graphics still suck, though. Now I've purchased Uncharted on the Vita, and played several demos. Though I've heard many complain about the graphics in Uncharted (and I can see what they mean) it looks beautiful compared to Ys. Ys is by far the worst looking Vita game I've seen yet.
Story is so different from either version of Ys 4, it's pretty much a whole different game, and has very little to do with Ys 4 - other than some common characters and tunes.
And speaking of the music, I'm not really sure what's going on there, either. So much of the same tracks are reused throughout the game (always the same town music, for instance, even though Ys 4 had several different town BGMs). Yet, I've already heard a few brand new tracks that aren't even from Ys 4... while there are still so many remaining Ys 4 tracks to use. I'd really like to hear as much of the Ys 4 soundtrack used as possible, though it's looking a lot like a lot of tracks are going to be excluded at this point.
Still, everything is overshadowed by how much fun the game is. Dungeon designs are great, new characters are great, combat is great, optional quests are generally worth doing, and uncovering the map is fun (Famitsu was right about that). You guys had better get a Vita...