One thing I haven't noticed in any of the commentaries I've read so far, beyond the general comments from the Nobel committee itself that, "Both scholars have greatly enhanced our understanding of non-market institutions," is people commenting on the similarity between their work. Williamson is primarily known for his work on explaining how corporations (firms) exist in part to help overcome market failure due to monopolies caused by the specific nature of many production processes (i.e. people who make engines that only work in Ford cars can only sell them to the Ford company and vice-versa), while Ostrom is known for her work on how local groups of people can overcome market failure due to shared ownership of limited local resources.
In my Sytems of Survival-coloured view, both Ostrom and Williamson's work represent efforts to understand how people have developed innovative ways of coping with situations where guardian ethics (that deal with monopoly and limited resources) come into conflict with commercial ethics (that deal with trade of goods and resources).
More on both of these folks at some point in the future...