I hope I am not abusing my welcome on this thread with my suggestions! :-)
You may or may not want to add this small suggestion in future versions, but it might be nice from a usability perspective to have the 'select system to show' filter icon pull down a list like the 'favorites list' or 'hidden games' icons do. This is a quicker interaction than opening up a new dialog box and then selecting the item and double clicking it or confirming the selection.
Is it this way because EmuCon dynamically adds systems and it is difficult to do this in a pull down? or perhaps it is to allow the selection of more than one console in a filter at a time? If it is the latter, I think if a user is not listing all they are probably looking to choose one system in particular at that moment.
What do you think?