No performance reasons, but I could not get the filters to render correctly in hidpi resolutions. I'll try out your assets on the retina MacBook and see how they look.

Looks good. I thought from the comment you had switched to filters, but it still uses the pseudo shadows, so it has no effect on hidpi.

Thanks for the clean up.

I wanted to switch to filters, but I was thinking there are some reason for not to use them. I will send another pull request with filters ;)