Question about 100-300 "new" vs "old"

I have heard that the new version of the 100-300 is sharper. My question is this, is this a new physical lens or is it the firmware update that took place in January. I also heard that using the electronic shutter on the G5 makes stops shutter shake and improves the sharpness at the long end. My only problem with that is that it also greatly slows down multiple exposure mode. If it is a new physical version, how do I know if I have the older or the newer model?

Thanks

--
Ann Chaikin
Painting & Photography:
http://www.annchaikin.com
http://annchaikin-photography.blogspot.com/
http://www.flickr.com/photos/annchaikin/
Photo a Day
http://www.blipfoto.com/ArtistAnnie
Family Websites:
http://www.chaikinsofbellingham.com