If you're looking for a hotel, chances are you'll go searching for reviews from other consumers before booking. My Lecturer applies the same logic to university, allowing you to rate subjects you've done and browse reviews left by other past students for courses you're considering.
There's lots of obvious caveats with a site like this. Right now, there's not a lot of reviews on there, so you might not turn up any useful information on your prospective courses. Different students work better with different styles, so trusting a single review won't necessarily reflect your own experience of the subject in practice. For many degrees, you're stuck with compulsory units and pre-assigned tutors so there's not much value in getting depressed about them ahead of time. And as you get more specialised in a given department or faculty, you're likely to form your own opinions about individual staff members which will outweigh any anonymous reviews.
If you bear that in mind, however, this could be a useful resource when you're trying to weigh up two competing subjects, or wondering if everyone else thinks your lecturer isn't quite up to the task. My Lecturer is free to use, doesn't require signup.