The new G5 corded looks amazing, having weight balance adjustment and a 2000dpi scanner. Looks like this scanner is even better than the mx1000, making the 518 look outdated. It also uses the whole usb bus now apparently. Looks like my next mouse. 
http://www.logitech.com/index.cfm/products/details/US/EN,CRID=2142,CONTENTID=10715
http://www.logitech.com/index.cfm/products/details/US/EN,CRID=2142,CONTENTID=10715
