I have seen some crappy jobs painting and some very good painting jobs, it all depends if your willing to buy the right products and put the time in for the proper prep.
the problem with doors that have vinal that is pealing off is you have to take it all off then sand it properly, prime it and then paint it. it is also best done with a sprayer so its a lot of time and renting of tools if you don't have the right sprayer. replacing the doors is pretty easy but costs a little more money in exchange for you doing minimal work.