The back of my Iphone 4 needed to be replaced due to breakage from dropping it.
Also I needed to clean my three year old HP-laptops inside from dust and I am planing to open up my Xbox 360 and clean that too.
The switch went really smooth and easy.
The time consumed to do the actual repair is like one minute maximum, just unfasten the screws with the pentalobe 5 bit.
Pop the old back out and put in the new one, make sure its secure and fasten the screws again.
Why pay someone a hundred bucks to do it for you, when you can spend 120 and get all the tools needed to 70% of all your future repairs?
Also it came in really handy when opening my HP Pavilion DV5 to clean it out with high pressure air.
I have done this before but these new tools are just such a delight to work with, it cut my time in half doing this cleaning routine.
Apart from the base toolkit, I used an Itawa Silver Jet air-compressor unit and a airbrush nozzle to get all the dust out without having to worry about damaging the delicate parts of the computer.
To do the switch on the Iphone its really easy and simple, if you have any doubts or worries check the guide or search it on youtube.
My laptop is a HP Pavilion DV5, but if you learn how to open one HP its really simple to learn the rest as well.
Just cause it is creaking like it is about to break it is not necessarily so, but being causes is usually better then having to fix the plastic and cheaper then buying a new piece.
If it is your first time opening a laptop or an HP product I recommend checking out the guides on this site, also youtube again is golden cause seeing and reading is totally different things.