I have the gorilla arm too. I don't use it much, and don't know anything about the others available, but for what I've done with it, it has been more than satisfactory to me. Maybe I just don't know what I'm missing with the better models available.
If you want a great arm for the money, buy the Lone Wolf arm & an extra extension arm. I loved mine before I got my 3rd arm. 3rd arm also make a mini version that looks very good also!
I really like my Muddy arm as well. Having a good fluid head is more important than anything else IMO, also make sure your arm is strong enough for your camera.