I liked it, the gunplay actually felt pretty satisfying with the sounds and the way the shells dropped.
some feedback:
1. the audio seemed to be rooted in space, so as you moved around the music would move all over the stereo field, making a very weird experience in headphones
2. since enemies dont drop money and the money is instead a pickup it didnt feel like there was much reason to kill the enemies, i found myself just running by them to grab the $ to afford an upgrade i was close to. i think enemies dropping a little money would be cool.
3. the weapon variety and feel was really really good.