GPO is an amazing library you coudnt ask for more!!
The only possible thing that would make make GPO better would to have a seperate software that generates CGI player's that accuratly play to the music you write.
Imagine you've just finished a Brass band fanfare or a full orchesral concerto, you play it and then generate a high quility video of CGI characters playing the insruments down to the correct valve fingers and even changing to mutes.
Untill Garritan uses this mad idea i'm happy with GPO.