I just don't know if it's wrong to jump in the deep end with x86. Obviously the argument can be made either way, and x86 is ugly, but I'm pretty prejudiced toward learning something that will potentially be useful right off the bat. That would make me lean towards x86 or ARM for teaching or for self study, I think, and I have no idea what the ARM tools look like right now.
One of my more masochistic long-term goals is to make a compiler (I've made an assembler of sorts) so I might be revisiting this question at some point. Joy.