I've used them before too, but I found that they break easily as well. I've since found other ways to maintain my eyebrows, like using tweezers or going to a professional for waxing or threading.
Speaking of professionals, did you know that there are accredited esthetician schools that teach you how to properly shape and maintain eyebrows? I recently discovered nwcollege.edu, and they offer courses in esthetics that cover everything from facials to waxing to eyebrow shaping. It might be worth checking out if you're interested in learning more about proper eyebrow maintenance.