In Denali we made a small (but significant) change to the Find and Search syntax. By adding a new optional argument “NotFoundValue” you can tell DAX to return a value instead of returning an Error when the value is not found. In 2008 R2 DAX would always return a Error.
What is the benefit ? When you use the find or search function in a calculated column and it will return an Error for one row it will return an Error for all the rows. To solve this you have to wrap the Find or Search formula with a =iferror() to actually be able to work with this formula. Another benefit is that you don’t have to work with errors inside the function, this can degrade performance.