Personally, I like the idea of plugin interfaces having some form of visualization. The compressor example is obvious. So is the graphical equalizer.  I can imagine other cases as well: waveform of a sampler. Perhaps a synth that let's the user scribble their own waveform.  There are all sorts of things that would provide better user interfaces if the control is richer.

This web UI stuff might be the best new interface we've never used. But, I want a studio configuration, not some "I can change plugin parameters using an html text input while I'm at the office."  David seems to think anything with a pretty interface is stupid and just eye candy. But try convincing Apple's human interface team of that argument.

If the solution to visualization in lv2 is "ur doing it wrong", then perhaps we are using the wrong plugin tech.