We've just spent the last few days making a video to advertise some new social features we've just added to our product.  We filmed it all using Nokia N95s and amazingly it worked incredibly well. 

We were concerned the quality would not be up to it but had no discernable frame drop out and the quality of the result was excellent.  We still have a version which is good enough to play out on TV but sending it to You-tube lowers the quality anyway.  For me the real advantages were less obvious:  we often had members of the public in the background and they were not put off at all by a group using their phones to take pictures, whereas I am sure with a big camera you would not get such natural performances.  For me this was the big bonus.  One thing we did struggle with though was that to start with we were filming with more than one phone to get different angles of shots, but when we attempted this we were always getting the other camerman in the shot - in the end we had to stick to one camerman.