I think you'll get to part of the answer if you ever try to write a compiler that targets x86, or if you write an x86 machine emulator, or even if you try to implement the ISA in a hardware design.
Although I understand the "x86 is ugly!" arguments, I still think it's more fun writing x86 assembly than MIPS (for example) - the latter is just plain tedious. It was always meant to be nice to compilers rather than to humans. I'm not sure a chip could be more hostile to compiler writers if it tried...
The ugliest part for me is the way (real-mode) segmentation works - that any physical address has 4096 segment:offset aliases. When last did you need that? Things would have been so much simpler if the segment part were strictly higher-order bits of a 32-bit address.
