This is REALLY a powerful tool in harmony creation!
Just started really using this lately instead of Harmony Engine EVO and the quality of the pitch algorithm is obviously better. The ability to have the plugin actually create the harmonies instead of just processing in parallel is a songwriters dream.
There are some issues with Sonar specific to correctly detecting pitch and position when you drag the clip into the interface. It will put the clip WAY out of range. A workaround, for now, is to choose the 'arranger' tab and manually drag the clip to the right spot.
From there you hit the harmonize button and you have a huge variety of harmonies and scales to play with. I've discovered that since it relies on the clip that you drag into interface, it works better if you make a dupe of the track and pitch correct that first before dragging it into the interface of the plugin.
I've been corresponding with Tim on the Zplane forums about the issues with Sonar and he has been incredibly responsive so far so I am hopefully they will get resolved so that other Sonar users can benefit from this killer tool!