Promoted parameters for materials
Editing materials in unreal involves recompiling/saving each time, but its considerably longer and more irritating than a quick recompile of a vop network. There's something similar to promoted parameters to avoid compilation (called 'parameters'), but to use them you need to create instances. The houdini analogy is if you were to promote parameters on a vop network, but then to use them, you have to create an HDA out of your vopnet, create a new instance, and you can only use those promoted parms on the new instances (and only within the vop network editor, not 'on the front' of it).
Scripting via UnrealJS
It's now available as a plugin directly in the unreal asset library, I've managed to make it say 'hello world' and create text that displays in game engine, but nothing beyond that yet.
Houdini to prototype blueprint
On a fast gaming laptop blueprint is still a little too slow to use interactively. The basics of blueprint, especially in terms of texture operations, maps loosely onto vops. I've been doing experiments in vops to work out uv operations, then use what I've learned there and recreate networks in blueprint. There's an irony here of using Houdini for realtime feedback on realtime shaders, because the shader editor for a realtime engine like Unreal is too slow for my impatient needs. :)