How is the 'Too Cool for School Protoge Pencil'?

I've noticed a lot of people use the Too Cool for School Protoge Pencil for under-eye makeup!

I'm thinking of trying it too, but it seems like I need to get a dedicated sharpener separately.

I'm also thinking about just using the under-eye liner I have at home...

Has anyone on Unpa used this?

If you've tried it, which color do you use?!