Cond question first - performance appraisals are subjective by the nature of the exercise. You can establish goals, metrics, and measurements all day long, but there is always an element of an appraisal that rests on how well you and your boss work together - mutual respect, trust, a good work ethic, etc. Those are hard things to measure.

Now let's look at different formats:

Self-appraisal: people are generally harder on themselves than their bosses are. Also, the individual rating themself knows their work and accomplishments better than anyone else.

Peer review: IF (and it's a big "if") peers are able to provide this feedback in an honest and non-threatening way, it can be very powerful. We all wonder how we appear to others we work with - what do they really think of us? If a boss gives us bad feedback, we can write it off - he's just a nasty boss, he doesn't really understand what I do, etc. If we hear from everyone we work with that we're perceived as a slacker, it's hard to slough off that feedback

• top-down review: this is a one-on-one with your boss, and it's your opportunity to hear what the boss thinks of your work, get some "quality time" with him/her to talk about your career path, where you can grow, and so on.

• 360 review - the most difficult to implement, and the most comprehensive/rewarding feedback mechanism. You hear from everyone - your boss, your peers, even your subordinates if you have them. You learn how you're perceived as an employee, a colleague, and a boss. This provides the most clear look through the eyes of others, and can identify weaknesses that the other types of reviews cannot - for example, a top-down review might not clearly identify weaknesses in your management style the way that a subordinate review in a 360 process can.

• Hope this helps - good luck.