As every geek knows, the demise of the Google Voice iPhone app marked the start of the Apple-Google wars.
Barring successful FCC arm twisting, Google Voice customers must use the mobile web app with the iPhone.
The good news is it's much better than the last time I looked at it. In my testing today it was very responsive. In fact, it was faster to use for placing a call to Canada than GV Mobile, the native app I've been using.
The GV web app follows RESTful principles, so I save a phonetop bookmark for a specific call. In my case, I can create a bookmark that takes me directly to the call setup for my regular Canada call.
To complete my regular long distance call I tap the bookmark, tap the "call" button (or SMS) then choose the calling number (defaults to my mobile) then tap call. I tried saving the last screen so it would be a 2 tap operation but it didn't work. So it's 3 taps, but it's significantly faster than using GV Mobile (but not quite as quick as using the long defunct GrandDialer).
It's not nearly as good as the dedicated iPhone app we aren't going to get, but for my purposes it's pretty decent. Note phone search only returns Google Contacts with a phone number.