I didn't solo until I had roughly 100 dives under my belt and was adept at maintaining good bouyancy. I probably wouldn't have started solo diving then if I hadn't had a string of boat buddies that disappeared as soon as they hit the water. In effect, by diving on boats with strangers for buddies, I was diving with all of the liabilities of using poor buddies and getting none of the benefits of the buddy system.
So I started diving solo. Not on every dive, not on deep or challenging dives. I dive solo in familiar, shallow environments when conditions are such that I can predict a relatively uncomplicated dive.
As for training and gear configuration, I practice redundancy and routinely practice gear removal and replacement underwater. I also carry at least two cutting devices that I can reach with either hand. As almost all of my solo diving is in water shallower than 30 ft, I don't carry redundant air. I'm considering a pony, but haven't gotten one yet.
I like the solitude that solo diving provides. I enjoy the lack of structure and my ability to explore on my own pace, to practice skills for as long as I'd like without feeling like I'm taking up somebody else's valuable dive time. I like the fact that, once I learned to slow down and hover, I started seeing much, much more underwater life.
I also like the mindset that solo diving requires. Attention to detail, focus, self-reliance. Yes, we should have those traits before ever entering the water, with or without a buddy, but solo diving requires them to a greater degree.
I understand the reasons for buddy diving and agree that the buddy system can be helpful in the event of some types of emergency, especially entanglement and OOA situations, and for that reason, I usually dive with a buddy, but for many of my shallow, near-shore dives, solo diving just makes more sense. That being said, I don't think it's for everybody and think that it should probably be discouraged until a diver has a pretty large repertoire of dives.
Safe ascents to all,
Grier