Insanely helpful - and I have only just installed it! Along with tt_base, this adds a number of key facts about nodes you'll find in the various inventories (creative or otherwise) when playing Minetest. Things like the luminance (light level) and whether a node is climbable or not are particularly useful I've found.
In addition, if you use Unified Inventory, you can also search by things mentioned in the description too - such as "luminance" to show all light-emitting nodes, and "climbable" to show all climbable nodes.
This is a must-have for all Minetest players: both creative and survival alike!