re: Has Opportunity actually seen any Dust Devils?
No dust devils have been spotted by Opportunity nor are there many dust devil tracks visible from orbit at Meridiani Planum.
However, features made by wind are plentiful, mostly in the form of tails coming off craters. Opportunity was very close to the largest/darkest tail trailing off of Victoria when the cleaning events occurred. This recent JPL press release image shows the Victoria tail and Opportunity's position at the time of the cleaning events.