As another data point, I'm in the process of transitioning from a Manfrotto 405 to an Arca Cube and I have to say I'm not yet completely sold on it. For one thing, the 405 has geared movements on all three axes of rotation whereas the Cube has geared movements on only two, which is a bit less convenient for me given my method of working.
I also find the Cube's geared movements aren't linear in terms of the effort required to turn the knobs;
i.e., it takes more effort to turn them when they're close to the middle of their range than at the ends, which is sort of annoying, as fine movements around the midpoint require me to use two hands to turn the knobs on each side, rather than one hand to turn the knob on just one side (and this isn't related to the friction adjustments, either, as mine are set at the minimum). Of course, I bought my Cube used, so perhaps this idiosyncracy is unique to this particular unit and not representative of Cubes in general. (Rod Klukas has offered to check it out for me and get it fixed if necessary, so we'll see.)
Overall, though, I suspect I will ultimately embrace it -- what it does well, it does very well indeed! -- but if mine is anything to go by, it's not without its quirks.