You can do everything you can on your regular. Text, call, voicemail. Plus, you can have it setup, so Voice text messages only go to the app and not your regular text message box.
If you're doing dirt, all you do is give the side chick(s) your Voice number only. Download App Lock, so you can lock the app with a PIN. Adjust your Notification Settings for the Google Voice App, so you it only shows a text has been received but does not show the actual message in your notification panel. That way whenever the side chick texts, it goes to the Voice app and only you can access it with the PIN you setup on App Lock. And even if your chick has your phone, all she sees is a blank text message notification going to an app that she can't access and phone number she can't track.
**this is all alleged information**
**don't ask me how I know all these steps**
**I'm the good guy**
Peace