This sucks.... you in!
At least one action (healing I think) is lacking a confirmation sound, and it would be nice if killed monsters left a shadow entry in the party roster so one could have a better overview on who's gone missing. And it would be useful if there was a clue on which monsters on the map are enemies (for example the AP dots could be red or their tile background). Also, when the collection list is open it would help if the buttons for "retreat" and "end turn" would be grayed out.
It does have quite a bit of depth in strategy actually, even though sometimes it's hard to differentiate some options that seem to have the same properties once in a while (usually there is a difference, like their elemental type, range, or strength, but these are very subtle); at least I think there were some combinations which seemed to be the same.
All in all it looks very polished and complete, and it has this "just one more turn" factor.