I think many people have the misconception that appraisal isn't a standard part of teachers jobs except for OFSTED. All teachers are appraised throughout the year by members of the senior management team observing their lessons. As well as this other collegues, teaching students and support staff regularly observe lessons.
The problem with OFSTED is that teachers are frequently critcised for things that they have little or no control of. A music department that I know of was recently inspected and critisised for things such as: other subjects using their room, lack of computer facilities etc. etc. If the managment team of your school is not prepared to sort these things out then you are fighting a losing battle.
I haven't yet had to go through an OFSTED myself yet but have lived through two of my mum's. Not a pretty sight! Being inspected is extremly stressful because everything is expected to be perfect, this is not a realistic expectation in teaching. There is simply not enough time in the day to do everything, so somethings have to give. Planning is extremly time consuming, as is preparing resources. As a new teacher I spend a large amount of time preparing worksheets, laminated cards, assessment sheets etc. Next week whilst I am on half term, I will not only be moving into my new house but preparing a new scheme of work along with worksheets, arrangments, backing tracks and preparing all the paperwork to set up my new brass band.
If OFTSED were to come into my department at the moment I know what the weaknesses would be: poor accomadation, lack of ICT at key stage three and few extra-curricular activities. I am attempting to rectify the situation in the one area I can. Mostly thanks to staying in school late and working in holidays and weekends.