Go in the products listing, change the dropdown on the right to display all sub elements. Then, sort by quantity and you will be able to easily see the products without much stock. Also, in commercial editions, there is an out of stock notification plugin in order to notify you that there are out of stock products.
Regarding advanced reports, like sales performances per products, that's something we want to work on this year. In the mean time, you can already have some limited reporting with the widgets of the dashboard and our integration with google analytics.