I love this plugin--it saves a lot of hassle, wading through the database, and manually changing database fields in a way that may or may not cause more trouble than they solve.
However, it looks like it changes all the GUIDs in the posts table. The WordPress Codex warns against this: "It is critical that you do not change the contents of this field." http://codex.wordpress.org/Changing_The_Site_URL#Important_GUID_Note
Can this plugin be updated so it continues to edit the other sections of the database, but not the GUID column?