I've been playing Shadowgrounds (got it as part of the Humble Frozenbyte Bundle), and it's thoroughly mediocre. The voice acting is bland, the enemy design is cookie-cutter, the story is generic aliens invade earth colony, the settings are standard futuristic outpost, even the weapons are pretty standard (Pistol, pulse rifle, flame thrower, rocket launcher, mini-gun, etc.) It's not a bad game, though. The controls work, the weapons are all useful, the graphics are functional (the lighting is actually pretty good) and the soundtrack is decent.
The actual complaints are mild. The enemies are dumb as bricks, but that's okay for an overhead shooter. The difficulty is rather uneven, and likes to try to be hard by spawning enemies out of nowhere, inside the range of your motion tracker (though off-screen, except for those climbing out of vents). There are some clipping issues, and it's a little too easy to get stuck on corners. Plus, the ceilings of buildings don't turn transparent until you've stepped inside, so it's hard to know if there's something inside ready to maul your face off.
There are no manual saves, and no mid-level saves, so you've got to finish a mission in one sitting if you're going to make progress. Missions can take more than a half-hour to complete. This is not good game design, IMO. Plus, the way deaths are handled is... odd. You get five respawns per mission. When you're brought back, it's at the last spawn-point with all the enemies you were fighting still riled up. It's possible to respawn right in the middle of a cluster of rocket firing enemies, though this is rare. More often I've come back to find the enemies I was fighting dead from explosives, an auto-turret, or after-burn from the flamethrower. For most missions the 5 respawn limit is very generous (I'm playing on medium difficulty.) I've only had to restart a mission twice. Once was the second to last level (which loves to lock you in a small room with a slowly spawning supply of highly damaging enemies), the other was due to a bug when the boss monster was killed while I was respawning.
Overall, I had some fun. It's not a great gaming experience, but I don't feel like it wasted my time.