UI: Ugly, like a synthedit plugin with "wood" paneling. That said, there are no menus, and everything is accessible and easy to see/read/use. Even the calibration controls are on the front panel, and the mirrored layout makes a lot of sense! An extra feature that shows how much effort was put into it is that controls will go transparent if they aren't influencing the sound, which is REALLY USEFUL.
Sound: Surprising. There are a lot of "FSU" and "LOFI" synthedit plugins out there. This one really stands out as a gem. From a simple subtle tape flutter on a piano bus to full out warbling brian eno-esque synth pads, there is nothing else that can achieve quit the same effects.
Features: Everything to do with pitchbend, wobble, wow, and flutter, this has it. You can have multiple variations going at different speeds, with multiple time modifiers per, as well as operate it in a L/R configuration, or use it as tape style flange!!! It goes from authentic vibes to crazy layers just by moving some sliders.
Documentation: Not needed. Turn it on, pull the sliders, and enjoy! Presets: There are a few presets, which give you an OK idea of what this plugin can do, but I've never used any of them. The best sounds are made by starting from scratch and tweaking for each song! Customer Support: It's freeware, so don't expect a call center. On the flip side, I can't think of any reason you'd need it.
Stability: Use it regularly in ableton live with various buffer sizes. It never causes issues, and has a very low CPU hit.
If you like the sound of old electronic albums, with warbling loops and bending pads, or just want a little bit of vintage widening on a guitar track, snatch this thing. It's a freeware gem.