Ryan Robinson, the City's demographer, has put together this map showing where Proposition 3 (10-1 representation) received its votes:
I don't think there's any surprise here. Suburbanites -- and even central voters south of Lady Birdy Lake -- concluded that they're not well represented by the central-Austin-dominated Council.
10-1 did poorly in west Austin and the central neighborhoods north of UT. A cynic might claim that these voters opposed 10-1 because it will dilute their outsized influence on City Council. I'm an optimist, though. I'm confident all those Tarrytown and Hyde Park "nay" votes were spurred by the fear that 10-1 will lead to ward politics and more NIMBYism.