The Jargon File (version 4.4.7, 29 Dec 2003):

winnitude
 /win'@?t[y]ood/, n.

    The quality of winning (as opposed to winnage, which is the result of
    winning). ?Guess what? They tweaked the microcode and now the LISP
    interpreter runs twice as fast as it used to.? ?That's really great! Boy,
    what winnitude!? ?Yup. I'll probably get a half-hour's winnage on the next
    run of my program.? Perhaps curiously, the obvious antonym ?lossitude? is
    rare.