I recently signed up for iTunes Match, and over the past week I've been in the process of uploading the majority of my library (~120GB). I turned iTunes Match on on my iPhone 4, and so far the only thing it seems to have done is slow down the responsiveness of my Music app enormously! Backing out of an album into all-album view takes a VERY long time, to the point where I'm occasionally convinced my phone is frozen. Scrolling is occasionally very laggy as well, nothing that I've come to associate with my iPhone. Will this lag time get better once my iTunes Match upload job finishes, or my phone finishes caching the Match results, or something? Or am I cursed with this very unresponsive iTunes Match library forever? Turning on "only show cached artists and albums" doesn't seem to really change anything. If this persists, I don't see myself using iTunes Match very long on my phone. Say it ain't so!