I love my Genesis cutter, although it hasn't seen really heavy use yet. Just did about 20m of Porcelain (can't remember the make, but they were pretty hard). The rails do bend, if you try to break the tiles by applying pressure, but when you flick the heel of your hand onto the handle, the break nice n easy! 😉
This info's a bit late for you i know, but might be useful for someone else... 😀