I went with my husband and my little sister (she was acting as our excuse to go...she was 17 at the time so I don't think it convinced anyone!)
The lineups may be bad on the best summer days, especially on long weekends, so if you plan on visiting this on your vacation, do find out about the holidays and come on a regular weekday!
There is a bus/subway combination that you can take there--ask TTC (Toronto Transit Commission, the local public transit) but if you have a car, that's a lot faster, probably not less expensive though with parking and stuff.
The roller coasters are amazing--especially the one that takes you first up and then whisks you down via a corkscrew up to another side; stop and then the same corkscrew back your back first...
The food is horrible and expensive and you need to walk a bit, but if you love roller coasters, this is your spot.
There is a fun looking water park too, but I never had time to try that but you might want to take your swimming suit with you.