The wiki as it stands is pretty terrible. It takes several minutes to apply a single update, and as a result, it's almost never updated. The information there has very little context as to what version it applies to. Most people I've talked to that try to use the information they find there find it is more confusing than helpful.
I'd like to propose that instead of using the wiki, the doc directory in the cassandra repo be used for docs (already used for CQL3 spec) in a format that can be built to a variety of output formats like HTML / epub / etc. I won't start the bikeshedding on which markup format is preferable - but there are several options that can work perfectly fine. I've personally use sphinx w/ restructured text, and markdown. Both can build easily and as an added bonus be pushed to readthedocs (or something similar) automatically. For an example, see cqlengine's documentation, which I think is already significantly better than the wiki: http://cqlengine.readthedocs.org/en/latest/
In addition to being overall easier to maintain, putting the documentation in the git repo adds context, since it evolves with the versions of Cassandra.
If the wiki were kept even remotely up to date, I wouldn't bother with this, but not having at least some basic documentation in the repo, or anywhere associated with the project, is frustrating.
For reference, the last 3 updates were:
1/15/15 - updating committers list
1/08/15 - updating contributers and how to contribute
12/16/14 - added a link to CQL docs from wiki frontpage (by me)