My personal experience and opinions on split keyboards is a bit different than those that have already commented.

I daily drove a Lilly58 for about two years. Switching to the ortho layout took some effort, but not enough to be a deterrent. And with capable and customizable firmware, any keys that were missing on my layout were made easily accessible with layers.

Having a wider shoulder stance felt nice. And being able to adjust the rotation of the boards on any given day to accommodate my posture felt good too.

However, there were a couple of factors that eventually got to me and caused me to switch back to a TKL.

First was the dynamics between mouse and keyboard. I use a mouse with my right hand. Grabbing a mouse then quickly switching my left hand to the right split was awkward. And hovering my hand over the center of the keyboard was not possible. I tried adding a trackball between the two halves and switching hands as needed, but getting my left hand to cooperate was a much bigger hurdle than I expected.

Second was the lack of hand movement. (I think what most find to be a benefit.). Over time I found that my hands would get tired and I would start making a lot more mistakes while typing. It took a while to figure out, but stretching my fingers to reach things like the function row and using my pinkies to reach for the standard modifiers actually gave me a reason to move my arms and wrists and not hold them in the same position for long periods of time. For me, maintaining position and the lack of movement was far more fatiguing then the stretching.

I don’t doubt for a minute that splits are great and that there are benefits to using them. I just think that how much benefit is very personal to the individual using them.