It's annoying not having caller ID, but it's worth the hassle of not worrying about going over on minutes. If you have my phone number you are someone I would answer for anyway. With GV you can also set it to force blocked calls to announce their name before you take the call.
I tested it in the sense that when I first got it I had it turned to pass the number through and it ate up my minutes like a regular call. If you are going to do that, may as well have them call direct and avoid GV.