There are several cons to using nitrogen tanks as compared to owning a dive quality compressor, IMHO. First and foremost is economics. I can buy a new Alkin, Coltri MCH6 or a used Bauer for $3,000 or less. Other than oil and filter changes, I have unlimited air for a lifetime. Let's assume I get tired of this hobby in ten years. My used Bauer or new Alkin or Coltri will still be worth approximately $2,000 if not more. That means I've gotten unlimited fills for around $150 per year including oil and filters. If I rent a nitrogen cylinder, my rental expense and refill costs are spent whether I use the gas or not. In addition, there is the inconvenience of storing a large cylinder, plus the added expense of a regulated fill yoke and hose which is at least $400-500 additional cost. I am at the mercy of suppliers who may or may not continue to supply nitrogen. I am also at their mercy to charge whatever they choose. This is sure to increase over the years I chose a compressor because I didn't have reliable dive shop suppliers who provide full fills at a reasonable price even though I live in a large city in North Carolina. In my case I'm not a super high volume shooter so I only run my compressor about an hour per month for 3 refills. The bulkiness and economics of nitrogen tank rentals just don't make sense for me compared to the cost of a dive quality compressor. The missing element in the equation is the residual value of the compressor. I also don't agree that reliable compressors are a $5000 investment. I have a $2,000 Daystate LC-110 which has been perfect for my requirments.