The user interface (i.e. the buttons) continues to be a problem. We get black labels on black buttons because molding the label into the surface is cheaper and more durable than painting it on. The ones that get me are the battery positive terminal indicators in the battery compartment. If you could just trust people to use the same mechanical connections we wouldn't need the labels.
Then there are the guys who think they'll be better than that and actually label the buttons with a contrasting color, but use a 4 point typeface that might be cool or stylish, but is actually too small to be read without a magnifying glass.
Then there is Epson, who devised a whole new set of symbols and meanings for the front panel of their XP-310 printer. The symbols are totally legible, but what the heck do they mean? Fortunately the printer broke down so I don't have to worry about it.