"The reality for me is that I see so many Ah counters wired wrong, programmed wrong, wrong assumed capacity etc. etc. that the Smart Gauge is going to be a great tool for many boaters who don't have the ability to use an Ah counter as accurately as they would wish.."

If a tool is used incorrectly, then it probably shouldn't be used. Actually I believe this also has some merit:

"It could also be argued that an accurate SOC is really all one needs to maximize cycle life of the bank and even at that it really only needs to be known once per day to adjust usage & charging..."

Now for the rest of it: the AH counters I have on the boat are Peukert and temperature corrected for calculating SOC, AH remaining, and time remaining - provided those numbers are entered correctly. They also reset properly at the top of charge (the ones I have are not cheap ones). But the SOC number is still not very useful, except for the sole purpose of maximizing cycle life and that is not high on my list of daily operational decisions. Even this is widely misunderstood: you may well get better economy (in $/AH delivered) discharging your batteries further than the universally recommended 50% though your cycle life is diminished.

When I am in the middle of the ocean, and want to decide if I need to start the engine to charge, SOC and battery cycle life have little bearing on that decision. I cannot change usage or capacity. What I want to know is how many AH do I have left at the current average usage, and how long will I need to run the engine to get them back to what state? All calculations done easily in my head in AH (and provided by the counter). If I only had the SOC meter, I have to guestimate capacity, guestimate replacement rate, guestimate usage rate, convert it all to SOC.

I have a cheap AH counter (Magnum) in my camper, and it certainly can be misleading if you don't understand its limitations. Perhaps the moral here is don't buy a cheap one, and learn how to use it.