Works very well - there is a soundset so things like pizz, harmonics, etc. all play correctly. Occasionally there is a keyswitch that has to be inserted, but the integration is pretty seamless. There is a ton of help on using GPO/ARIA within Sibelius on the Sibelius forum, as well. I've been using GPO with Sibelius since version 3 - and 6 is the easiest to use. I haven't upgraded to 7 yet, but that is simply because my machine isn't powerful enough.