One of the musical UI elements I always rant about (here we go...) is the global modular view, which is a way for a DAW to show you everything that's going on in your project. It should show the project's complete signal routing. This is particularly useful for electronic genres (as opposed to acoustic/instrumental genres, where the traditional rack-based paradigm is well adapted).

Here's an example: http://www.lazytrap.com/img/cut_four_isolated.png

Every DAW has an internal graph of how everything is routed together: the waves you put on your timeline, every effect and synth, etc. I just want that graph to be exposed, visible, and freely modifiable.

The problem is that DAW makers and users seem very attached to interface elements that are somewhat incompatible with this paradigm: mostly the track mixer and "insert effects". This requires the DAW to manage the routing behind closed curtains and hide everything behind layers of abstraction that I consider unnecessary and often opaque.

There's a variety of weird tradeoffs that are made to get modularity while still having these traditional features, like per-track modular views (eg. presonus), modular views contained inside plugins (eg. bidule, reaktor). While these are nice in their own way, I find that nothing can replace a global, freely modular view. The bee's knees is when you can nest it arbitrarily like Reaktor does (as a plugin). If I want a mixer, I can place it myself in the modular view.

Does any DAW do this? So far I'm using Buzz, which pulls this off perfectly, but has its own limitations (no good pianoroll, no arbitrary timeline placement...). From my rather extended foray into the topic, I've found that Mulab seems to fit the bill, though I'm not sure. Some software like Max/MSP, PureData, and Usine are 100% centered on modularity, but they cheap out on the "timeline" aspect, which I find very important when I'm working with lots of samples and video.