I do believe Cassandra requires a much more intimate knowledge of its internals if you want to do anything serious with it - more so than any other database I've worked with.

I have to agree. But with the clarification that it isn't significantly more. Spend a few days and you will be an expert.

And I think it's worth noting that the "serious" things you would do on Cassandra more often than not you couldn't do on most other databases.

I agree as well. However, it seems a common mistake to assume you can just "deploy", especially coming from traditional RDBMS.

Great power, great responsibility.

Some of what the article suggests (their own serialization format, using COMPACT STORAGE) isn't in or directly contradicts what the manual suggests to do. This isn't just a case where reading the documentation would tell you everything they found worked for them.