Thanks everyone for your perspective. I've maintained a high GPA throughout undergrad and I am confident in my ability, however, getting a good grade is't solely dependent on my doing the best I can; there are variables that are out of my control - how tough a grader the prof is, how helpful/understanding he is, whether or not he likes you and is professional enough not to let his feelings get in the way of grading you fairly. It's THESE variables that make me a bit nervous about having a whole year's expenses hang on the GPA.
Guess I'm in the right forum - decisions, decisions:)
Thanks again! Good luck to all of you confronted with difficult decisions