RPM packages (and debs of course) would be nice,especially now that cassandra is maturing and gaining more interest.
Lowering the threshold for getting cassandra running and getting started is also important.
I think the RabbitMQ project has an admirable "Download and install" experience, not to mention the rather cute "2 min guarantee". Definitely a good inspiration.
I've been studying Cloudera's Hadoop packages, which are very nice, and really appreciate the separate packages for configuration.
This allows easy deployment of node configuration to a cluster.
I'll have a spec file for building RHEL5 / CentOS packages ready for review and attached here in a bit.