After several months since Google acquired Urchin, they are offering free analytics service to all AdWords clients as part of their strategy to gain new clients and -indeed-keeping their existent customers and persuade them to spend even more on paid advertising instead of on a web analytics tool.
Strategically, for your business -and not for Mr.
Brin and Page's one- a web analytics tool shouldn't be attached to a service provider, as you would like to have an impartial measurement instrument and if at some point you decide to discontinue using this provider (AdWords in this case) to still be able to have the same capabilities.
Also, you would not like to measure just Google AdWords campaigns, but Overture, Espotting, 7Search and other PPC resources you may be using as part of your Media strategy, so if you'd need to have a different web analytics tool for the other Pay Per Click campaigns, you can also have AdWords on it, instead of in a Google-only atmosphere.
It's free, yes, but it doesn't mean this is the cheapest way to maximize our media budget and data management.
Other point to consider -if you are an Agency- is that Google's analytics does not allow Agencies to analyze their clients data on their behalf; it is for internal use only.
As a Search Engine Marketing professional, I'd recommend you to find a web analytics tool to track all your online activity and provide you with the feedback you need to get before taking strategic decisions, as for example ClickTracks (http://www.
com), 3 years in a row awarded as Best Web Analytics Tool by ClickZ.