A few years ago we had a thread in the tech forum, and IIRC, the original issue was whether Shearwater should offer AI on its computers, which were at that time pretty much 100% tech. Opinions were strongly against the idea, but a small group of individuals argued well in favor of it. I was in the majority in opposition, but my opposition was primarily along the lines of it isn't needed. A simple SPG does the trick fine--why add complicated and unnecessary technology?
Since then, most of my technical diving has been with sidemount divers, and they tend to like the AI. I see a fundamental difference, and I understand their preference.
When I am diving backmount doubles, I know first of all that I have way more gas than I should need for the dive, which is standard practice for technical diving. I should only have to be concerned about my gas supply if something goes wrong with my gear or if something goes wrong with the dive. So far neither has happened to me, at least to any significance, so every now and then I check my SPG to make sure everything is going along as expected. It isn't a big deal to do so, and I still do not see any reason to fork over the cash for an AI system that is not going to give me much benefit.
My sidemounted friends, on the other hand, get a real benefit. They have to change from one tank to the other on a regular basis, so it is a true benefit for them to have that information right there in front of them as they dive. I can see why they like it. I am myself trained in sidemount and have done a fair amount of it, but not much lately. I learned it for diving caves, and I have not done much cave diving of late. If I were to start doing that again with any real frequency, I can see myself giving the matter more thought.
As for decompression bottles, I don't see any need for it there. You are only on a bottle for a certain length of time, you should have way more than you need, and you should only have to be concerned about your gas level if something is going wrong.