I download a track or a podcast, start playing it in WMP and find that the tags are wrong or not filled in.
In Windows 7 this problem is compounded by a) the removal of the "Now Playing" node in the library; and b) the uncertain time period for a track to be added to the library ( from 0 to never ).
In Vista, the "Now Playing" library node allowed you to correct tags on files in the current playlist. This is often the time when I notice that tags are wrong. I suspect that this was removed due to a bug whereby editing some of those tags in this mode made WMP crash. Rather than fix the bug, the entire feature was removed.
The only workaround in Win7 is to right-click the track and choose "Open file location" and edit the tags outside of Windows Media Player.
The entire tagging interface in Media Player needs work.