The roots can become a home for assorted fauna, and they can provide asthetic benifit if you are pleased by seeing them. As a nutrient removal means, while they are certianly a solid nutrient sink, they simply increase mass too slowly to be of benifit in respect to water quality improvements.
They can be useful if you have 20 or so. They are also interesting and you will get many comments about them. They don't grow too fast but you will need at least 3-4 feet of space above them. They also do best if you mist the leaves with fresh water once a day or so.