List of valid units are below url are not valid.
https://developers.arcgis.com/javascript/jsapi/bufferparameters-amd.html#unit
The sample provided for unit is using constant strings from GeometryService class. But no all constant work ex: UNIT_SQUARE_MILES
I'm surprised that the documentation is linking the 9.2 EDN pages instead of the latest version of esriSRUnitType and esriSRUnit2Type. That said, why would you be using an areal unit (square miles) instead of a distance unit (miles) when specifying the how large the buffer would be?
Ken,
My bad I should not be using areal unit.
But regarding document bug I personally think unit should point to GeometryService class constant section. And that section should also include numeric value.
I used the "Report an error on this page" link found on the bottom of each documentation page and today received this reply
This has been updated for the next release.
There will be a link in the unit description that takes you directly to the constants table.
When you come across problems in the documentation, please use that link to report it.