Hi GetBent,
I had a Quest (the Q45's predecessor) before building up my S40. The Quest was really heavy, but since I only used it for flat commuting, I didn't mind too much. Then the S40 came out. I sold the Quest, bought the S40, and have been a happier camper ever since. Right after I built up the S40, CB announced the Q45, "coming soon." I was nervous that I would want it more than the S40. But when I saw how similar it was to the Quest, I thought "whew. The S40 is it." The S40 has enough tire clearance to run nice, big, cushy tires that I run tubeless at about 40psi (I use 42c Panaracer Gravel Kings). The lack of rear suspension isn't an issue. While I said earlier that I can go just about anywhere in town on my V20, I will add that the S40 is still a noticeably different and easier-to-handle ride, especially at lower speeds. I have to pay more attention on the V20.
I use Zefal Spy mirrors, left and right, on all three of my CBs (I have a S30 as well). These mirrors are great because they are small, out of the way, and durable. I strap them on near the bend in the handlebar, allowing me to still grip the brake hoods as an alternative hand position.