Overall, I like the document - for now, I only have a few high-level comments:

1) Introduction was great.  Might want to use some bullets to separate out the questions in the third paragragh.

2) A diagram illustrating the relationships of the primary services in OGSA would be helpful in the future - derived 
from the relevent paragraphs in the document.

3) Security is stated as being very important - glad to see that.

Keep up the great work!