I had only implemented n/p so far because that's all I used, but I've added j/k now. I'm aiming to match Google Reader's core functionality (except the social side), so I've made a note of its keyboard shortcuts, and will add more over time or as they're requested.

Thanks for your comments regarding the design! I'm going to try to keep it as minimal as possible mostly because that's how I like it, but also so that it can be drop into existing site designs without too much hassle.