From what I've observed most people have a love/hate relationship with it. They love how long it makes their lashes yet they hate how easily it clumps.
I have it and yes, it makes my lashes waaaay longer than any other mascara I've used before. The trick to applying it without clumps is to use a very light hand (that means no wiggling the brush like you would do a regular mascara) and to get all your coats done before it dries. An eyelash comb helps, too.
I'm rather surprised by how natural looking this mascara is. It's not super black, more like a natural black.
I don't know how it compares to other fiber mascaras. This is the only one I've tried so far.