In a previous life i was a area manager for a well known retailer. We used to do appraisals every 6 months.
The employee was given the form to self mark using pencil, the range was 1-5 covering excellent to unacceptable. You then got the form back early enough to study prior to the appraisal meeting.
I only ever had 2 instances where the employees opinion of their work differed wildly from the company. The appraisal score was only set in stone during the actual meeting with the employee. It was all very useful, concise and left no grey areas where improvement was required (if needed)
