Now that you’ve obviously purchased, installed, and started playing with your Windows 7 client, you’re probably fantasizing about all the great things that will happen to your environment when you upgrade all of the machines in your site / OU / domain / basement to Windows 7 as well. Let me tell you, it’s going to be great. Why? Because you’ll have GP Preferences client side extensions installed already in all of those Windows 7 clients! That means that you can map drives and push out shortcuts and add printers and configure power plans for all these Windows 7 machines from your own Windows 7 client (with RSAT) or with Windows Server 2008 R2.
To answer the question in the title, NO, you do not need to change your update your Active Directoy (if it's at least 2000, when Group Policy came about) to take advantage of sweet new Group Policy features and settings. The exception is if the application that the setting is relevant to requires an AD upgrade, like BitLocker. This is a good article on configuring BitLocker in your AD, written by the guys on the Directory Services team: http://blogs.technet.com/askds/archive/2009/08/18/bitlocker-and-active-directory.aspx
Also - check out an overview plus good getting started tips on this website: Group Policy Management for IT Pros. If there was anything in the above paragraphs that you have questions on, read this article first. Seriously.
Have fun! Go Preferences!