Personally, I feel B&W photos convey a certain mood or feeling that is often lost in color photos. When viewing B&W, your attention is more focused on the contrast and detail of the subject, the way the light falls on the subject. It also leaves a little more to the imagination, which can draw you deeper into the photo.
As far as color goes, I believe it is beneficial when you have a subject where the color is the main focus. If the color of the subject isn't a key part of the photo, shoot it in B&W to capture more mood in the scene.
An example might be a scenic shot. Generally, I prefer to shoot in B&W to capture a more artistic feel to the shot. However, if the scenic shot includes a deep blue sky with brilliant white clouds and a foreground with some colorful flowers, I will definitley shoot it in color. Otherwise, I'm sticking with B&W.
These are just my opinions, and I am sure there are others out there that can help out on this a lot more than I can.
im partial to black and white as well. as chase said it does add to the contrast,...but for me it allows the viewer to respond more to the heart of the subject matter, kind of like what it is and what the viewer wants it to be instead of just looking at it and saying "yep, thats what it is..."