That was seriously the best cliffhanger for a finale, with them in the Impala and then suddenly them getting impaled by the fast-ongoing truck running them down. The most interesting factor is how "Bad Moon Rising" is playing, an upbeat kind of tune, while the Winchesters are unconscious and bleeding until the screen goes black. What a way of enticing people to want more from the show. Very clever, and it saddens me that the show hasn't done anything like that since.