I'm new to sidemount myself but after a few dives and a class with Steve Lewis (Doppler) I find that my reasons for getting into it are valid and found a few more besides once I actually got the rig on and started diving it. First of all I strongly suggest that if someone is going to do this that they take a class from an instructor that not only can teach the class but actually dives SM on a regular basis. There are numerous schools of thought on how to route and configure hoses, set up the bottles, the bungee system, set weighting, choose cylinders, and get it trimmed out. I was lucky in that I had no preconceived notions and even though I've watched Jill's video a few times and set my tanks up according to it, I went into the class with the idea that I knew nothing about it. I did have some of my wreck diving ideas and gas management ideas and they were ok. In fact I learned a new way to teach my gas management for diving double tanks period in the class and will use it in my Advanced and Intro to Tech classes.
I had my own SM rig - a Dive Rite LT tech that I just got, a pair of LP 75.5 steel cylinders, and my HOG regs set up with the hoses I had on hand. After the class I changed the neck clips, got rid of the ring bungee system, and changed two hose lengths. I might have come to the same set up after a dozen dives or so. And maybe not. But the class allowed me to bypass those experimental dives trying to work things out on my own and gave me a real head start on a proper set up.
Sidemount is not just for exploration and tech dives. And frankly the gas management is relatively simple for any reasonably intelligent person. And for the person who has been properly trained as a diver in general. That will unfortunately leave a bunch of people from the "be back with 500 psi" school needing some serious remediation. It does require to pay more attention to their diving than most vacation divers want to. But it can be done easily and successfully with a little practice to build muscle memory and get their thinking where it needs to be.
But for those like Tracy who have back, neck, knee, shoulder, etc issues or strength issues it is a perfectly viable solution. You don't have to sling two 80's. Hell sling a couple 40's or steel 45's or 50's and you have a nice light compact, highly streamlined system. Set the bottles in the water or hang them on a line off the boat, get the harness on, jump in, clip on, and go. Surface unclip the bottles hand em up or clip to a line to be pulled up and all you are getting out of the water with is a harness.