Wonderful analytics, albeit expensive to get the premium service. Word of caution though, their stats are not accurate representations of what's what. Its web traffic reporting only uses data collected from computers with the Alexa toolbar.
Very very helpful tool, especially if you're running an online business. It may take some time to get to fully understand how it computes the stats, but all one needs to know is to interpret them and utilize them to strategise
There have been several negative reviews, but I have had nothing but excellent service from AdWords so far. It has cost our business quite a tidy some in marketing budget, but I think the results are worth it