Scholarships in general and Ontario Trillium Scholarship in particular
The Trillium scholarship is very good.  The only scholarship I know of that's worth more is the Vanier ($50,000 for two or three years).  The Vanier is open to both Canadian and international PhD students as long as they're studying at a Canadian institution, so it's extremely competitive.  The Trillium is only open to international PhD students studying in Ontario, so the applicant pool is a bit smaller; however, only 75 are awarded each year, so it's also very competitive.

Two other typical scholarships are the NSERC PGS/CGS, which pays between $17,300 and $35,000 a year, and the Ontario Graduate Scholarship, which pays $15,000.  In my department, about a quarter of the people who apply for these scholarships will win.

As for the the other part of your question, when applying for a post doc position, scholarships certainly won't hurt you.  Your publications are more important, of course, but since the Trillium application includes a "plan of studies", winning it suggests that you will be able to win grants in the future.  A scholarship won't make up for a lack of publications, but it can give you an edge over a similar applicant who didn't win one.