When it works it's a really nice toggle switch with interesting wiring possibilities.
Had some issues with mine after about a year of normal use and ended up replacing it with another EP1111. So far so good, this new one seems to work just fine. However, I've read that other people have been having problem with this product as well, which makes me think that DiMarzio might have some quality check problems with this certain product.
Otherwise it's a sturdy toggle switch, nothing on the outside is wrong (nothing came loose or anything), so I guess the fault in my old EP1111 was internal of some kind.