I cannot say I like or dislike using pre-cuts. I think for some, beginners, it is something you can get and make something that coordinates and make it quickly. They can build confidences in new quilters learning how to coordinate colors and patterns.
Most pre-cuts are of good quaility material and shrinkage is minimal, so after making a top it can be washed and any shrinkage would take place then.
Washing material is great in larger pieces, especially dark colors that you fear will bleed, but I have used the color guard cloths and have so far not had an issue with the fading of dark to light colors.
Pre-cuts are higher in price for convenience of course. Knowing what you are making and the amount you need is essential, should you need more later puts a hold on finishing your project unless you are able to subsitute! But all in all, pre-cuts can be fun and a learning tool.... just my thoughts mind you :) .