The debate over the merit of such tests will no doubt continue for the forseeable future, although I don't quite entirely agree with Blue Foot. However, this subject has been done to DEATH. Regardless of what anyone thinks, if you want the job, then it is simply a part of the selection process at the moment. You can either whinge about it, or prepare, perform and hope for the best.
Soup: Can't speak for JQ specifically, but can tell you the results are instantaneous. When you are advised of said results depends on other considerations (number of other applicants being processed, whether or not they are scheduling interviews sooner or later, medical results/drug test etc...). Might take a couple of weeks.