SETI@HOME to me is a chance to contribute to a project that may possibly provide proof of extraterrestrial sentient life. There is a very large sky to survey, and I believe this will take quite a while.
Concerning the SETI project overall, one must realize that the sheer size of space which fills our night sky vastly out weighs what has been examined so far. Most stars are so far away, that the light and radio wave signals we receive from some has been traveling through space much longer than the whole human race has existed. Therefore, I am not at all concerned that we have not yet found evidence of extraterrestrial intelligence. This will clearly take a very long time. We have only been listening for a short time. Signals may have already arrived before we started listening; or they may not arrive for a century or tens of centuries. The galaxy is vast and the speed of light is very slow compared to the distance that must be crossed, and in terms of our human lifetimes.
One must also acknowledge that intelligent life is likely to take many forms. We are searching for life as we know it to exist, and therefore we search for communications methods that resemble our own. We also search the sky in star systems that we believe offer the greatest mathematical probability of detecting intelligent signal sources.
As our knowledge of nearby, almost invisible brown dwarf stars increases, we have to allow for the possibility that we are searching the wrong part of the sky. Our search is based on many assumptions which may in the future prove to be erroneous. For example, the communications method may be wrong. We know that laser light has a very high bandwidth, and that it provides a much more efficient medium for transferring large amounts of data. Laser transmission may not be it either; perhaps a quantum transmitter and receiver are more efficient for communicating across the massive distances of space which make light speed communications far too slow, and we simply don't know how to build one.
In a nutshell, in my humble opinion, we have not found what we are looking for because we have only searched a small fraction of the total area we need to search, we have not been listening very long, and it is possible we don't know where to look and/or we don't know what to look for. This doesn't mean that life and communications methods similar to our own do not exist; it just is likely to take a very long time to detect them. Perhaps many centuries. So we should keep plugging away even as we come up with newer ideas, faster methods, and better tools to conduct the search with. It's the best we can do, and the potential payoff is so huge.