I just heard a fantastic piece by Thomas Bergersen which was done entirely with samples, many of them being his own personal set, which I had to share. I'm amazed not only by how good his samples are, but how well he crafts them to make them sound alive.
This particular track is so well done, that I do not think I would notice that it's not a real orchestra if I wasn't listening very closely. Even then, it would be very difficult if not impossible to tell. His attention to detail is phenomenal, and should give us all something to strive for to achieve in our own sequenced tracks.