http://www.macworld.com/article/163658/2011/11/itunes_match_what_you_need_to_know.html

http://www.macworld.com/article/163606/2011/11/check_your_musics_icloud_status.html

Between those two links you should find answers to your questions =)

For the ones that have errors, just try again by right-clicking and selecting "upload to iCloud" (or something like that) -- all the ones that had errors after the initial uploading worked fine on the second try for me.