This stream has been very helpful to me, as before I started watching it (which happened to be the week of the first Beginner's Corner episodes) I was only maybe slightly above casual players. Now, I actually know the basics of what's necessary to play above the casual level, and the meaning and significance of terms like okizeme, overhead, blockstring, and meaty.
Now that I'm motivated to play the game more seriously, I just need to get a new video card so I can play against others and figure out how I compare against those around my skill and what I can work on (other than completing combos).