The pros are basically what they said in the ad. They eat debris, leftover food, and dead plant matter. The cons would be that they are considered pest snails. They breed like crazy if there is excess food in the tank and they are hard to completely remove from the tank. Many people consider them unsightly, especially once they are in larger numbers. You will likely get them in a tank at one point of another if you buy plants from LFS's, some people do like to introduce them intentionally though. In my opinion nerite snails and apple snails are much nicer to look at and much easier to control the population, and they essentially have the same benefits.