I think it's a great tool. I use a workout protocol developed by Dr John Jaquish for his x3 bar (actually, I just purchased it too). It is a pretty extreme workout but just 10 minutes a day, 6 days per week.
The Gorilla Bow is capable of doing his complete protocol and is less money. I am getting the x3 bar mostly because it seems right since I use Jaquish's protocol, and because it would be slightly easier travel with.