The 65816 is a fascinating chip, even though it's a dead end in the evolution of home computing. It falls in a category with the Z8000 and maybe even the 80286: backwards compatible with their predecessors, but extending them in odd, idiosyncratic ways. Processors evolved and mostly discarded the vestigial weirdness of the original 8-bits, but its a special kind of fun to revisit assembly language programming in that style with some of the oppressive constraints (address space, addressing modes, minimal registers) lifted.