Solid game, but it has serious lag and stability issues with certain weapon upgrades and/or combinations.
The Double Machine-gun upgrade causes graphical lag when firing the weapon, and it becomes incredibly hard to control the ship. When I stop firing, the ship goes back to normal and I fly into an enemy bullet because I swung my mouse hard to the side.
Same thing happens when you have the Quad Cannons upgrade or the Barrage Homing Rockets upgrade.
Not sure if the unstable ship is a gameplay thing or not, but the graphical lag is a huge problem.