I only finished the main story of the first one and didn't bother finishing the optional stages. There are tons of things to do in the first game even after the story but I got tired of the grind already.
The title sounds somewhat familiar to me even if I never have heard any of my friends talk about it or saw anything about it online as far as I know, but I looked up the first version and it looks good to me. I'll probably pick up that first and see if I like it and if I do I will definitely buy this new one. I'm really liking a lot of the games being shown by Playstation at E3 so far.