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Pro's and con's to retaining access. This was a con.
That said, only one of my clients ever actually wanted access to his account, and once we set up some reports to be mailed to him every week, I don't think he's logged in once. In fact, now that I think of it, that was an existing account that I took over the management of, so he always had access to it. I kind of specialize in people who either can't or don't want to be bothered with the details and want someone to handle things top to bottom.
I have found that this willingness to share information has circumvented problems when you just can't get an account to go. The client feels like they are partners and that you have worked the hardest you could for performance.
I have never experienced a client twiddling with things that I set up. I am on their account every morning. If they want to pop in and see the stats in the dashboard great. AdWords is so complicated, that clients simply want to see not touch has been my experience.
The clients that are micromanagers (I've ready Perry Marshall's book and know what to do) as simply not selected by me to become my clients.