Are there any plans to expose the PropertyGroups API through the web services API? Being able to let other applications search content through the custom properties we set up would really make PropertyGroups very useful to me.
Yes, you can search by property groups using WS (in theory almost!) The property groups API it not fully exposed by WS. I'll study if we can inluse this improvement in the next release.
Granted, that query will also return items in the Trash that contain the searched property, but I think I can add a clause to the Xpath to suppress that.