I've been doing some of my GCSE's in Year 10, so I can talk about specifics here.
I was hoping for A's for Science, History and RE before the exam, and I was hoping for an B in my English Lit exam.
But when the exams arrived, my sciences were still strong, but the exams alot harder then the Mocks, and History and RE were long exams and my energy burnt out quickly.
So now, I'll be blessed if I get an A for Science, B's for History & English, and RE, well I'd be relieved, yet dissapointed with a C!
Overall, I think B's and above are good grades.
Obviously, it didn't go exactly as planned, but you never know. Next year, I'll work 10X harder.
The wait is annoying me too. I'd rather see it on a computer screen instead of waiting for the paper in a queue of all my friends.