[jackhammer]

Most data scientist these days use scikit-learn or R. Weka is really out of fashion. Mahout and mllib are difficult to use and perform less. Often it's better to just down-sample or rent an EC2 instance with a lot of memory.

[platypii]

Weka is definitely more old-school, but it has a LOT of algorithms available. Weka and Mahout are the two biggest ML libraries on the JVM, but we couldn't find any direct head-to-head comparison so this was the result. In the future we plan to also add scikit and mllib and more in the future.

Your point about being difficult to use is exactly the problem that Algorithmia solves.