Having been on both sides of many performance appraisals (both good and bad) for over thirty years now, I feel they do more harm than good. What do you think?

As in just about everything involving management, it depends on your manager. I found my most recent one to be quite useful - he raised a coupla small concerns, which he was right to do, and which I've tried to fix. I also had some concerns, which the whole team is slowly fixing. I got some realistic goals for the next year, some of which have since become unrealistic, others I've already hit, and a couple which I've not yet done.