Here is a few things I have found:

* There is no option to play my playlist. The following bugs were found when using "artists similar to..." option.
* After typing in artist's name, the plugin will often show "Playlist is empty" message or something similar. Retrying the same artist usually works.
* After playing a song, last.fm plugin stops playback until a button is pressed.
* The skip-forward button that is supposed to skip to the next song does not work very well: I have to click it multiple times before it works. The button gets highlighted, but nothing happens.
* Audio scrubbing does not appear to work, at least no audio files appear in "My downloads".