Having just complted my first month at the OU, first quiz and first assignment, I thought I'd update this thread for those looking at the OU:
The study syllabus is sraightforward, easy to follow, etc. It gives time frames for reading groups of chapters from the book you're on, as well as the due date for any assignments and quizzes coming up. You can work on the assignment as you read, and the quizzes are small (10 questions). For the quizzes, you have 2-3 attempts at each question which takes some getting used to... obviously with a computer marked quiz it isn't at all flexible on the answer (for myself, with the math questions its right or wrong, obviously no partial credit for correct work, etc). But they only count for 2% of your final score. The assignments count for much more.
I will say the pace is pretty intense. In 20 days I finished the entire first book (from the image above, Global Warming) some 200 pages. Now, as of tomorrow, we move on to the second book. So the important thing is to keep up with the study guide and don't fall behind, or you may find yourself playing catch up with half a book of information.
One Saturday a month you will have a tutor day at the local uni for about 6 hours as well in order to meet your classmates, ask questions, etc.
All in all I am enjoying my experiences with the OU.