The trophy doesnt promise you some big banner film with Bollywoods superstars! Everyone benefits in this show by getting EXPOSURE. That is one of the main reasons they all take part in BB...
Sometimes you dont even have to be a winner to get big offers. For example, Sana khan got to work with Salman in Jai Ho but did it really do something major for her career? No...so its also about luck i guess...nepotism rules Bwood so it's not necessary talent and looks will take everyone far...But I think almost all BB contestants became household names and got some sort of work to do...
Regarding Gauahar: Her debut as a lead heroine is supposed to release in a year or so (she got the offer before bb7 though) And there is something else shes shooting for but hasnt revealed anything about yet...Other than that, I believe it was a major boost for her career as she got to host Rawstar, IIFA rocks, do more modelling shows,a popular music vid, various performances etc...and most importantly, she has a solid fan base/support now...considering she was almost invisible or unheard of before BB7, I think this can be called success ...
Are u just asking this so Gautam's victory doesn't bother you? :P don't expect him to become the next shahrukh khan, but his career graph will definitely look better than before!! that'll happen even if he doesnt win... :)