i'm not adding any answers to this, but i have to agree. i haven't broken any pieces yet, but the center corners are a huge problem. i tend to solve slower than i could in order to make sure i don't break anything. the center edges occasionally decide to rocket across the room. no big deal, but i did happen on a plane last week. luckily a guy was watching me solve and he found it and gave it back to me.
it may have something to do with how much it is lubed. i have never gotten my 5x5 to be anywhere near as fast as i'd like it. i bought another can of lube last night so we'll see if that minimizes the center corner issue.
lastly, when you guys are lubing a 5x5, do you take it COMPLETELY apart like you would a 3x3? i've been opening up some of the top layer (yellow), spraying lube like crazy, putting it back together and then repeating on the opposite side (white).