It has been very effective for a number of projects in which I have been involved. I have seen many circumstances where a company "had tried AdWords and it didn't work", but were very successful when it was implemented in the right way. One of the key points of a good implementation is limiting the ads with the right negative keywords, locations, and even the time of day. You need to be creative in linking your product with your customer's expressed need that might not necessarily be on the top of your list as well. Think about what your customer might search for prior to even knowing that a product like yours exists. For example, a customer might look for a spreadsheet template for managing some process and not even know that your software helps manage that process more effectively than a static spreadsheet. When you hear the stories about AdWords not being effective, you can bet most of those were implemented incorrectly...or the product wasn't meeting an expressed and acknowledged need of the customer.