Yeah, immediate mode seems like a perfect fit for a DAW. I see a lot of common misconceptions in the article. It seems like this is mostly an opinionated list of hypothetical issues imagined by the author, not something backed by a lot of data gathered from implementation experience.
Yes, I also agree that the author is wrong to dismiss immediate-mode toolkits. Immediate mode would be my first choice for a DAW application. I even would say it's almost a no-brainer as it makes so many things easier. You would need to be careful when rendering data-heavy widgets (ex: wavform) but the approach goes a long way with some careful planning even without necessarily implementing complex texture caching etc.
