Andrew O’Hara, Apple Insider:

There are two primary issues with the port on the new iPad Pro — one that can be at least partially overlooked, and the other is going to be a show-stopper.

And:

The biggest criticism of the case was the requirement of having a full back cover that added unnecessary bulk and weight on an otherwise slim device. I’d have preferred a two-piece design that allows for a removable keyboard with an optional back cover.

As it stands, you are stuck with both a keyboard and a back cover, or neither. If you wanted to remove the keyboard but keep the back, sorry, that’s too bad.

And:

Second is the poor adoption we’ve seen from outside companies, which the shift will not help. Apple touted at launch that third-parties could make use of the port, and they even reiterated strong support with products in the pipeline just last year. Now that the port has completely moved, anything in the works based on the previous port location is dead-on-arrival.

Tough investment for a peripheral company to deal with a complete redesign of a hardware interface. Not just moving a port/connector, but completely changing the way it works.

And I’d add to this issue the problem of putting any sort of case over the Apple Pencil magnet/charger. You have to find a way to convey that functionality with your case, no easy task. And, given the likelihood that Apple is not done innovating here, it may be some time before the functionality of these ports stabilize.

Wholesale change is tough business for a peripheral maker.