They feature music, video, and podcast support, and come with Wi-Fi and FM Radio.
Wi-Fi is used for wireless synchronization and for sharing photos, podcasts, and music with other Zunes, although shared songs may only be played three times by the receiving Zune.
Positives and negatives mimic those of the Zune 80 and 120, as the 4, 8, and 16 are very similar devices in a smaller package: the Wi-Fi, user interface, and excellent sound quality are praised.
[1] Some reviews have mentioned the lack of TV shows in the Zune Marketplace, it has since been updated with the ability to purchase and rent TV shows and movies.
[2] The specifications as listed by the official web site of the Zune:[3]