The issue with the iPad now is more than ever the limitations of iOS.
Lack of mass storage support (actually it's an arbitrary limitation. Pretty sure the OS would support APFS, NTFS, exFAT,...)
Lack of control when it comes to multitasking (Apps in background may get halted, offloaded,...)
Lack of input (yes, for some stuff a mouse is still the best choice, although, the pencil often comes close)
Lack of proper external screen support.
crippled Bluetooth stack.
[...]
Apple also needs to drop some of its guidelines for serious Apps/Games. It should be perfectly acceptable to require certain accessoires for certain apps.
Anyway... can't wait for OSX on ARM... That should solve those problems once and for all...