A lovely app, and I applaud the developer for keeping it free.
However, Rename (and perhaps my idiosy as well) caused a major problem. Using the OS 10.6 Finder's own 'Make Alias' command, I made a new folder located in the Documents folder that only contains aliases of all my applications (for use as a launcher in Classic Menu's Apple menu). However, that process added ".alias" to the end of all my applications' names (e.g. "Safari.app" became "Safari.app alias"). So, I used Rename to remove the last 6 characters from all of my applications' aliases, but that resulted in all my apps (not the aliases) being converted to FOLDERS because Rename removed all of the ".app" extensions because Rename performed that operation on the WRONG FOLDER: Even though I dragged and dropped all of my applications' ALIASES from my Classic Menu Items folder into Rename's file list, Rename ignored those aliases and instead renamed everything in my Applications folder! Now I have to use Rename again to add back the ".app" extensions, but then I must go through all of them to fix the name of all the folders and ReadMe files that were in my Applications folder when I ran Rename.
My point is that this is powerful software, and it can majorly screw up your system if you don't test it on a few unimportant apps, folders and other files before you batch-Rename anything. Lesson Learned.