I don't hate the iPad Pro. I kinda like it when I'm lounging at home. But the main reasons I want to sell my iPad Pro is because it never lived up to its "Pro" name for me. (Not you, or you. Me.)
My biggest issues:
Lack of App Support - We went through the initial excuses of "Just wait for devs to catch up" but, as often happens, the devs showed us how little they care for the Apple Watch, Apple TV and iPad Pro. So, not only are many apps lacking split-screen support. I still have a few that run in that little iPhone sized box.
Awkward Multitasking - Side panel multitasking is an inefficient price-is-right wheel of apps. And full multitasking is pretty much two windows that awkwardly require reaching back and forth. I know some people love it but I never could adapt.
Mouse Support - You can see the trend here. I'm not hip enough to change my ways to this world of oversimplified computing. But yes, I want a mouse. Highlighting text, dragging capture areas, precision accuracy. I'm not sure why people resist this fact but keyboard shortcuts and mouse input help streamline a workflow. So without these then its hard to call a machine "Pro".
Portability - Big is great for the couch but its awkward for travel. In fact, my "solution" to all my issues (Multitasking, Portability, Multiple Windows) was to actually get an iPad Mini to carry around and to use at home next to my iPad Pro.
Anyway, I've tried and given up on selling my iPad Pro. The base price is just too ridiculously high so impulsive Ebayers tend to avoid it. So I'll wait a month and see how the market looks.