For me the most important selling point for th petrel is tht you dont need a manual to use it for any diving related operatons. Ther is no middle right 2 left and hold the right fin above your head to change gasses. Now for some , changing gasses is some sort of technical thing. For anyone knowledgable,,, sitting on the boat and changing from air to ean32 predive is a gas change. In additon anyone that has ever had to work the dongle to get data from the puter to thier laptop knows the value of the blutuooth interface. Next the ability to use almost any battery that will physically fit in the hole. The cost is less than many upper end computers. You can adjust the amount of conservitism that works for you best. or just leave it at 30/85. Ther is no padded data to protect the stupid from them selves. All rec computers should behave like this. I havnt so much as said a word about the tech side of it if you want to call it that.