I've found the more annoying part of d% systems is more when you GM them. It places a lot more pressure on the GM to figure out what the proper difficulty to things are. For example a 30 in a skill is typically presented as a somewhat basic level of proficiency, but applicably it only succeeds a third of the time. Obviously you have to keep in mind that some tasks are simple enough that you can had a few degrees to their rolls, but it still seems a little annoying to have to manually consider these additional layers to the game.