Is this gravel stabilizing underlament an effective product?
Yes, it is used in construction somewhat commonly. There are a couple of different situations where I have personally be involved with its use:


Soil stabilization for large fills - In areas where the ground is soft and heavy construction equipment needs to move (e.g. access roads) it can be placed in layers and filled with soil to help distribute the weight of the equipment without forming ruts.
Gravel parking lots - Similar situations involving parking lots and gravel are used to provide natural water infiltration while still providing a surface that is less likely to rut.
"Invisible" roads - The fill material can be modified slightly to support grass growth. This has been used to provide lawn areas that can support fire trucks for emergency access in all conditions while not having to pave a road up to a building.


All of these situations are similar in that they provide for a distribution of wheel loads on soft or wet soil. 

In summary, these types of products are used in construction, so they are equally applicable home use.