But seriously, it's nice. Your buddy twists your hand a bit meaning "go up," waves it back and forth meaning "level off," etc.. All you do is sit there and vent gas when necessary.
I don't know whether I can say definitively whether a maskless ascent is real world training or just a drill to ingrain and practice for taskloading. What I do know is that not being able to see clearly while doing a standard ascent or breathing from your buddy's primary is a tremendously useful drill for getting a grip on what an ascent should
feel like. When you ascend with breathing vs when you need to vent the wing. This is something that I will be practicing on every dive for some time to come (but with my mask on, thankyouverymuch). The other thing I got with this was a much greater overall comfort level with my mask off, even in cold water. I do know that I've been on dives where I wouldn't want to have a direct ascent to the surface as my only option, mostly due to overhead boat traffic.
you better be able to prove it to me scientifically and not "it's because that's how we do it".
The irony to the above quote is that the Essentials course that I took and that TSandM posted about would, at some level, allow you to prove this scientifically both to
yourself and with input from the instructor. On a whiteboard, at the surface, and in the water. As long as you are open to thinking about how buoyancy, weighting and trim are affected using a BCD vs. BP/W, you'd probably benefit a lot from it. This was more about trim than gear, though gear plays its part at this level and further on esp. with when diving as a team. And of course, configuration issues become much more critical at future levels.
The other thing I want to stress was that, in my class with Jeff, there was
not a single time where the "why" to some drill or configuration or planning was "because that's how we do it". Quite the opposite in fact, we were encouraged to delve into the details and explanations, even when the answer lies way beyond the level where we were in the class. For example, the reason for a left d-ring but no right d-ring has to do with how the configuration with stage or deco bottles will work, with or without a scooter, and that nothing they do at this level needs to be "undone" or "unlearned" for any later training. As another example, my classmate wasn't sold on the hog harness and long hose to start the class, and he may or may not go over to a BP/W for his normal diving, but he certainly understands the differences in how they affect his weighting and trim, and I'd be shocked if he didn't have a long hose for his primary the next time I saw him diving.
In the end, only you decide how much of the Essentials you incorporate into your own diving.