Not just vignetting... but also possible damage!
All EF lenses will fit a cropped sensor cameras, but EF-S lenses are potentially dangerous to full-frame cameras.
EF-S lenses are a little longer in the back (they go into the camera body a little farther in when installed). If you put an EF-S lens on a full frame camera and it doesn't give you an error code (it did not give an error code on an EOS 10D I tested with an 18-200 EF-S), the mirror will likely hit the back of the lens when it flips up... the next step in the process is to log onto Adorama or B&H and get a new camera (or have the mirror replaced).
I just noticed this is my first post here... on an 8 month old thread.
Canon EOS 50D | Canon EF 50mm f1.8 II | Canon EF-S 18-200mm IS | Vivitar DF 383 Series 1 | CowboyStudio NPT-04