Yet if the track is above 256Kbps, it will lower the matched quality.
But you can see the bitrates of all the files. It doesn't replace anything automatically, just be careful only to replace files that are lower bitrate.
Content only available via Apple devices?
iTunes Match also works on windows.
It has uploaded your songs to the server then. If it matches a song, you get the standard 256Kbps iTunes Store version.
That's if you play it from the server. It doesn't touch whatever file format is in your original iTunes library.
I don't understand all the hates about iTunes Match! It's been great experience and a joy to use for me.
Because other people have had results vastly different from yours. Depends a ton on your library content and how many songs you have.
Great idea, terrible execution.