I find hidden controls (on the top edge) a little inconvenient, to say the least. I like the controls to be easily accessible, especially the main power switch.
Another possible problem is accidental spillage of liquids when placing items into, or taking from the machine. I'm always careful myself, but I swear that the power switch and menu selectors on my Bosch have gotten stickier through time. I don't know if this is just a combination of general kitchen dust and steam from the machine, or whether it is foodstuffs (flour particles, etc).
The controls on my machine don't seem to be particularly well shielded against such ingress (hard plastic buttons, that 'wobble' in their surround). Other competitor machines have wipe-clean membrane type touch pads (like a microwave oven control panel).