I've thought about getting the OEM rubber mat for my Golf. The carpet with velcro blocks worked fine when new, but over time the blocks don't hold as well. I tried shaving the carpet, but it didn't do much good.
For Weathertech, I always hear great things about the floor mats. When I saw them in someone else's car, however, I wasn't impressed. They are more like plastic than rubber. If the rear trunk mat is also more like plastic, then it won't keep things from sliding around the way a rubber mat does.