I'm not fond of them. I prefer balsa or horse leather. Especially on the EP felt becomes messy.
I like the flatness of leather and balsa. Felt always gets bumpy for me
It works very well for deburring though, but I've been taught to sharpen and abrade the burr off. That's what I do now most of the time. When doing quick work, I draw the blade through a felt black just to make sure.