It's really exciting that every new DSLR now takes amazing, cinema quality HD video. One of the main reason it looks so different from video cameras of the past is the super shallow depth of field that large sensor sizes produce. It looks really cool BUT you will have to learn to manually focus the camera just like they have to do with movie cameras. If you are looking for a great tutorial on the basics check out the BTSV by Still Motion below.
How To Deal With Manual Focus And Your Super Shallow DOF