I have so far enjoyed using wikis since I was introduced to them last year. They are easy to use and extremely practical for people separated by distance. It is nice for collaboration because you can contribute to the wiki on your own time; you don't have to agree to meet at a certain time with your collaborators and work around busy schedules.
I enjoyed exploring the wiki on "Library Success". It has everything you need to know and what's best is you know it's created by people with experience in the library field who know what they're talking about.
I use Wikipedia a lot as a reference tool and I don't think any encyclopedia has it beat. It may seem dangerous to let just anyone edit content, but I think that for every crackpot out there who tries to vandalize a wiki, there are professionals who can step in and correct it. I think it evens out in the end.
The idea of using a wiki for collaborative note-taking in the classroom is interesting...maybe after using it awhile students could get a clearer idea of how to take better notes. Hopefully it would also foster the idea of teamwork.