Gutters are, in some ways at least, a double edged sword. Gutters work GREAT for directing the water where you want it to go so that it does not cause any problems for you. But the gutters tend to collect small twigs and leaves in the Fall and then you have to clean them out or the twigs and leaves will plug up the gutters and you will get spillage all along the gutter. Then too, the potential is there for ice dams, but if the roof and the gutters were done correctly it should not pose a HUGE problem.
All in all, gutters and downspouts are really good to have, just be aware that if you have trees around the building there can be some routine maintenance involved in keeping the gutters working smoothly. If the gutters are on a rather tall building, you will need a way to get to them in order to effectively clean them, or have some other way of cleaning them out.