DeFrank

Find out what your character's anti-air is and you can win about 1/4 of your matches right there.  
 
Never block a jump in, ever.  Not only do you miss opportunities to do damage, but you are training yourself to be crossup fodder.

I love Guy's play style.  
 
And by "play style", I mean "butt cheeks". 
 
EDIT: may as well put something useful in here as well,  http://www.youtube.com/watch?v=BiNzPpo4__Q

You don't necessarily have to jump, you can buffer it through with a HP or HK.

Yup.  
  
Negative edge Bushin throw FTW.

Getting a D in defense against a player that isn't a complete scrub will result in a loss, bud. 
 
Basically, in that scenario, you gave your opponent a ton of opportunities to do big damage, but they were too garbage to take advantage of or exploit your mistakes. 
 
It's still good practice to get in the habit of not making defensive mistakes. Win or no win.  The grades are not based on the result of the match at all. They are based on performance. 

@Plasma, @JokerSmilez: Apparently, Sweep cares since he started the thread. :)  
 
@Sweep: A good way to raise your defense is to make good use of "Option Selects". These are character specific and will take some trial and error but will make you a much more effective player when you play more experienced players.   
 
This video is very good on breaking down what it is:  http://www.youtube.com/watch?v=6CzpKOD1v1I&feature=related. Note that even though this video is for Zangief. ALL characters have  "Option Selects" and they are easy to find once you know how to look.

 I must say, at first, I was skeptical of Sony's whole motion controller thing.  
 
But now that I've seen a handful of games and heard the coverage from GDC, I am now apathetic.    

Demon's Souls. It's a shameful addiction.

That mess of numbers flying all over the place along with all that text and bars/meters does a great job of making an otherwise spectacular looking game look calculated and absurd. It's like they feel obligated to prove to you that things are happening under the hood.  
 
Info-Diarrhea.