I purchased the commercial version of this extension. I was looking for something to help me create some charts and graphs on my site. Found Plotalot and I was really impressed! I have been able to make some super looking charts and graphs for my website.
As the author an others have mentioned, you do need to know how to write SQL queries. However if know how to do it or you are willing to learn the results are easy. Simply create your query in your favorite SQL query tool, copy and paste the query into a new chart or graph, select the type of graph you want to use and save. You can instantly see the results in the component. When you are done it is super easy to insert the chart / graph into an article or HTML module.
I love the fact that this is a component. Other options I looked at were plugins. To me, I would much rather have a component to create and organize with.
Did I mention that it is really a great value for the price?
If you know how to do SQL, then you won't do much better creating charts and graphs than using Plotalot. Highly recommended!