Pretty good, but still some flaws in the gameplay.
Overall, it's a good game, with some interesting mechanics that help keep things interesting. However, there's still some things that are broken. For example, getting one-shotted by the mad bombers or the skirmishers - I found myself with roughly 90% of my HP, suddenly getting one-shotted by the a skirmisher around wave 16-18.
Healing is wonky - it stutters, stops, and doesn't really work properly. The tier 1 healing skill only actually heals you if you wait, then tap an arrow key to move. The tier 2 healing skill that lets you regenerate all the time works up until your health is about 90% full, and then it stops.
The tier 4 (hellburner) turret is absolutely useless; it does no more damage per hit than the tier 2 turret (impaler) and fires 5 times slower (1 shot every 5 seconds) - I bought it for one wave and then scrapped it because it was utterly pointless to keep.
Upgrading barricades seems like a waste of aether because the damage enemies do continually grows, to the point where a single striker can clear through a 100-HP barricade in two hits and a juggernaut can clear it in one by wave 18.
Fire-rate upgrades don't seem to affect single-shot physical damage weapons even when the instant reload skill is purchased. It would seem like they should.
So, overall, pretty good, but there's a lot of small issues that keep it from being great.