I haven't produced anything yet, as I have other stuff on my plate at the moment. But I snooped around the interface and absolutely love it. Everything is laid out in front of me, and it is really nice to have a list of intrinsic functions, render states, default.fx functions and what-not.

I was debating in my head the usefulness of such a program for multi-stage pp effects, and then I remembered how many times I've wanted to be able to see the output of each individually anyway, so I see its use there.

The preview window is very helpful, and being able to load in my own model and see the effects straight away was very gratifying. However, there are sorting errors for complex models, and changing the render states (making sure ZEnable and ZWriteEnable are True, and setting ZFunc to LessEqual) did nothing to help. Setting a Sky Cube makes the preview model invisible -- but only with the Normal Mapping example. Sorting errors are prevalent in all examples I tried. I wish I could tell you more.

Three additions that would be nice:
1. Multiple Techniques. I might be blind, and just couldn't find it, but there didn't seem to be a way to have multiple techniques in the one file. Fallbacks can be really useful, as well as the automatic LOD system with techniques, so it's a shame that isn't there.
2. Rotating the model in the preview window with mouse can be really awkward. The panning works great, but the tilting only corresponds appropriately with mouse motion when the model faces the camera. You may want to use quaternions to remedy this, or perhaps it's no big deal. But one more thing that's related to this: When loading new media (or perhaps just when clicking "reset camera"), it would be nice if the camera position took the model's bounding box into account (it can be a little annoying to load a large model and have it either fill the screen, or overlap the camera). Also, it doesn't seem to detect smallish mouse movements -- I suspect this is because of an enormous framerate causing time_step to round down to zero. Perhaps there should be a cap on the framerate?
3: For pp effects, it would be really nice to be able to use a preview image instead of a preview model.

Anyway, well done! This contest is already earning some really cool tools for the community! I can see myself enjoying it as a .fx editor more than anything else; being able to separate the pixel and vertex shaders into their own independent windows is tidy and charming, but I found myself lost not being able to see the input and output at a glance. I'm sure shader programmers who learn in this software will be able to appreciate it more than I can at the moment.

Jibb