It's alright.
It's a pretty fun mechanic, just run backwards and forwards while the game gets harder and harder. I played up until I died on the 19th nun, I didn't play a second time because running around pressing the spacebar only has so much entertainment values. What about unlocking new powers or weapons every few nuns?
I'd praise the graphics if they weren't a copy of Castle Crashers and every other game that's jumped on the 2d-cartoon-graphics bandwagon in recent years.
Oh, and you get flung waay too long and too far when you get hit. GEE WHIZ, IF THERE'S ONE THING I LOVE IT'S HAVING THE CONTROL WRENCHED FROM ME AND WATCHING MY CHARACTER GET FLUNG AROUND LIKE A RAG-DOLL. Honestly, flinging the player around when they get hit is ALWAYS a bad idea. Nobody likes that shit.