Recommendation: Recommended.
Description: Demonstrates building a particular variant of a 2,3,4 Tree (B-Tree of order 4). This AV is specific to 2,3,4 Trees and shouldn't beviewed as a 'typical' instance of how B-trees work in general. In particular, the rules for pre-splitting internal nodes on the way down during an insertion are specific to the 2,3,4 Tree.
Evaluation: Sophisticated use of pseudocode that can expand to show more detail. An 'Explanation window' describes how the tree works. The AV does not support the 'delete' op; it supports everything else well. As an extra bonus, you can pop open another window that shows the corresponding Red Black Tree (without pseudocode or explanation).