I liked it, it reminded me of some old-school shmups that I used to play as a kid. The main problem is that when I grew up and started to get older, I lost all my reflexes, and now I'm absolutely terrible at playing these games XD
However I enjoyed S-Hollow as far as I could go and I wish I could go further (maybe I'll try again for the challenge?). The gameplay is very good and the "enemies" are well done with good ideas. Nice concept!