I think it is very accurate. For the most part it has me pulling up to streets within what appears to be 10-20 ft, for the most part. I have seen it off by half a block or so, but than it seems to catch up. Might have been gps interference from the city buildings at that time, just a guess.
Don't know if you are aware of this but one of my favorite parts of Google's GPS is the ability to search for alternate routes.
Once you are navigating, click on the menu button, route info, then the button that appears to have 2 lines to one balloon on the bottom. That gives you alternate routes to your destination. At the top select which route to highlight. Road info, miles, and time will be listed at the top. When you look at the map it will have the traffic layer visible to aid in your selection. Awesome!
Google's GPS is like everything else android. Google puts out some really amazing software with very limited amount of instruction.
I would practice it around town and places you know for no kidding a couple of weeks. Things come up, lock ups, phone calls, etc...That way when you really don't know where you are you know how to handle the GPS instead of getting frustrated (experience talking here, lol).
How I handle phone calls is to place them on speaker when they pop up, home button, drop down the message bar from the top and select GPS. That way while you are on the phone you can see the map as you are driving.
Also, to everyone, a public service message. Please, just pull over if needing to spend more than a few seconds clicking around on the phone.
Hope it helps.