Great game, much like Frontiers, but improves a bit on the core gameplay. The progression now feels much faster and you unlock tower upgrades within the first few levels, which is a great change.
Also the inclusion of hero abilities was really cool, since it added more control over them. Everything just feels more balanced.

One thing that I missed from Frontiers was the boss battles. There was a few before the last boss, but they felt more like normal enemies just scaled up.

If you enjoyed the previous Kingdom Rush games, you'll feel right at home with this one.