Definitely, there are some...

* The icon resize is not handled perfectly: when icon`s new size does not fit
  into the layout, the icon just disappears (instead of being moved out of the tray)...
  Such situations are rare, though.

* Wallpaper changes are missed sometimes (for instance when stalonetray is
  swallowed by FvwmButtons). Workaround is to change wallpaper once again.

* Window size changes are sometimes ignored by WM.
