A couple of things it doesn't mention but are also definite benefits (for me anyway) are;
- Automatically opting out of any Service Provider "search" services (such as those offered by Virgin Media) when you miss-type a URL
- Avoiding any blocks your Service Provider might put on you reaching certain sites by substituting DNS entries. Of course the down side of using a service like Google is that suddenly by using a US-based service you are subject to US law and filtering
Here are the instructions in order to set-up your Mac to use Google DNS.
Go to the top-right of the screen and right-click the Network (Wireless?) network icon;
|Apple Network Options|
Select "Open Network Preferences";
Click on the "Advanced" button at the bottom right;
|Advanced Network Options|
Click on the "DNS" tab (centre-middle at the top);
As you can see in the screen shot the Google IP addresses for DNS are 188.8.131.52 and 184.108.40.206 (which are certainly a lot easier to remember than IP addresses generally!).
You need to remove any entries that are already in this box and replace them with the two IP addresses above.