How long does it take to download itunes match?

iTunes Match is a service. There is no software to download or upload. What is happening is your iTunes library is being mirrored in the cloud by iTunes comparing what is in your library to what is availble on the iTunes Store. Any tracks that are not "purchased" or "matched" will be uploaded. How long the process takes is dependent on the size of your iTunes library and the upload speed of your internet connection. Based on these two things the process can takes hours, days, or weeks. Just be patient.