This change seems to cause strange behavior for invalid HTML where there is an id attribute with a space in it. This isn't a problem if the id is properly formatted and doesn't have a space.
If an element has a space in the ID (it was being auto-generated on our side and it wasn't supposed to have one...but it did) then the find() won't return a successful result on a subset of the children nodes. In our specific case, a parent TD node had an id="FIRST SECOND" (example) and then the children of that cell was a table with a row and 3 cells. Even though I wasn't using the id attribute in the traversing or selecting of any elements, trying to find() the first child cell of the TD with the invalid ID attribute would always return an empty result.
However, I could do a find() for the second and third cells and they would return the correct elements.