For me he plan mode is as useful as ever, even though I understand this is just a prompt. For large changes there are few problems exist such as context window limit and compaction, and even though models got better these are still detrimental to models performance. I found making one large high level plan and then splitting it into N plans grouped around distinct areas and then running N implementations if possible in parallel, or some consecutively, improves model "vision" far ahead. The workflow author suggests might be more useful for prototyping, but there are still types of work that are better done with massive pre-planning stages. And of course running exploratory prompt a.k.a. plan is useful even for smaller types of changes like small features or bugfixes.