I think that a problem many people have in conceiving of life on other worlds is failure to consider the myriad forms it could take. Carbon isn't necessary for biological structures, its just the path life on Earth takes. Any reasonably stable element whose outer shell is only half filled can bond with itself to construct biological structures. Given this, the underlying problems within the Drake equation become more obvious.
1) The equation assumes life can only form on a certain kind of planet with a certain kind of star. If Carbon is not a required part of biology, life could arise on any planet, or even without any planet at all (asteroid belt, deep space, inside stars, etc.)
2) The equation assumes intelligenent civilizations must possesses radio. I don't even need to talk about the flaw in this one.
3) The final part of the equation talks about civilizations that are within radio range of Earth. If we are discussing the total number of intelligent species in the galaxy, this has no relevance. Bearing this in mind, please stop using the Drake equation as justification for a low-species argument.
Getting past all that, it is my belief that intelligence gives species a distinct advantage under certain conditions. In a stagnant environment, such as that found in a race existing in deep space, intelligence might well be harmful. However, anywhere there is competition or a rapidly changing environment, intelligence will be a help to a certain point. Once that limit has been reached, new strains will be necessary to enhance intelligence. For although people don't like to admit it, we are evolving. The human race has grown substantially larger since our ancestors only 4,000 years ago. Without a force to make us change, however, we will degenerate, losing mental as well as physical faculties as the need for them disappears. This is why an Eden is undesirable. Stagnation causes entropy, pure and simple.