Some Berkeley students developed a similar service called Ninja Courses[1]. This lets you browse through classes, order textbooks and also shows ratings. (Although all the ratings are submitted by Ninja Courses users, I believe.)

It can even automatically build a schedule for you by choosing lectures and sections that don't overlap, optimizing based on user preferences. For example: do you want more morning classes, more afternoon classes, more gaps, less gaps, some days off... This automates away a rather tedious part of choosing your schedule--something I haven't seen in other similar tools (although I haven't looked too closely).

Instead of shutting it down, the university used it to build an official Schedule Builder[2]. The official version doesn't have rankings, but exposes other interesting information--in particular, grade distributions.

Since then, Ninja Courses has expanded to a bunch of other UC campuses as well.

Just thought I'd share a nice success story to counterbalance most of the others :).

[1]: http://ninjacourses.com/

[2]: https://schedulebuilder.berkeley.edu/