The home button on my iPhone 4 was worn out. I would have to press it hard to get it to work. I purchased a cheap replacement home button from a third party via Amazon. I used the iFixit guide to install it. However, after reassembling my iPhone, I found that the new button worked, but it lacked the tactile click that the original button had. After a couple of weeks, I decided I did not like this. So I decided to pay a little more for the iFixit home button assembly. I installed the assembly and found it looks and feels just like the original! I am very pleased with it. It is very clear to me that iFixit parts are of a higher quality than those found on Amazon.
Both installs went very smooth. I had no problems.
To make working on your iPhone easier, be sure to get the right tools. The iFixit guide tells you which tools you need. None of the tools are expensive and can be purchased from iFixit, Amazon, or Ebay.
You do not need a Sim Eject Tool. A paper clip will work.
In steps 24 and 27, do NOT completely remove the large-headed 1.5 mm Phillips screws. Just loosen them enough to allow the screen to be removed. This will make re-assembly much easier.
If you are buying a Philips #00 screwdriver for this project, be sure to buy a good quality one that is magnetized. The magnetization will make it much easier to re-install the tiny screws.
In addition to the tools listed in the guide, I would recommend getting the following:
Jewler's Glasses (or some sort of wearable magnifying glasses). These make working on small parts MUCH easier. I have a pair that I got for $10 on Amazon.
Small 1" x 2" zip lock bags. I use these bags to hold the screws from each step. I use a fine Sharpie pen to label the bags with the step number and the screw size. This helps to prevent screws getting lost and/or mixed up. I bought these from Hobby Lobby for $2.