Here's how I use rename:
rename 's/search/replace/' *
And here's it in action:
oli@bert:~/Desktop/rawr$ ls
pie\u333.sh
oli@bert:~/Desktop/rawr$ rename 's/\\u333/PIE/' *
oli@bert:~/Desktop/rawr$ ls
piePIE.sh

Technical notes, and other ideas.
Here's how I use rename:
rename 's/search/replace/' *
And here's it in action:
oli@bert:~/Desktop/rawr$ ls
pie\u333.sh
oli@bert:~/Desktop/rawr$ rename 's/\\u333/PIE/' *
oli@bert:~/Desktop/rawr$ ls
piePIE.sh