I pulled this from a similar thread that was started in June, 2011. Thought it might provide some additional info.
Just saw this video from Aviation Consumer. It compares three types of tie-down systems; a home brewed system of steel pins, the Storm Force and the AID's (?) systems.
The steel pin system did not fare well in the test. The Storm Force system fared a little better in the sandy soil, but not up to manufacturers claims. However, by finding a more stable soil, they were able to reach the stated strength. The AID's system fared much better in the sandy soil. Here is the video.