i'd have to disagree with you, evil. your plants should be using the nitrate as it is produced thus giving you a reading closer to zero. high nitrates can inhibit plant growth. nevertheless, a nitrate reading of 10ppm isn't really going to cause much, if any, trouble. however, if it keeps going past 10ppm, it could mean that there is an imbalance in the aquarium, i.e. too many fish, or too much food.
regarding the use of fine filter pads and filter wool, i've heard that they are not really necessary and if you use them then they should be replaced frequently, as they'll contribute to a nitrates problem. i don't use them myself and my water is just as clear.