I am another 1 of the Oceanic VT3 owners. I am very happy with it. I used a Mares M2 for a few dives and found it to be a worth computer also but not air integrated. As for the redundancy question... Do we use dual SPG rigs? Are air integrated computer designed to replace the SPG? Aren`t the computers designed and engineered as safety devices? And my final thought is since I dive with a buddy isn`t it fair to say that my buddy`s equipment is my redundancy? As a diver I feel fine using my VT3 without a SPG as a matter of fact the main reason I switched to a remote air integrated computer was to eliminate an extra hose from my rig. I`ve taken this further with my gear and use a Sherwood Gemini auxilary secondary regulator/inflator instead of an octo so the only hose not streamlined on my gear is my primary secondary regulator.