Когда я был на Project Conference 2006 каждая демонстрация этой возможности сопровождалась почти что овациями зала. Казалось бы, что тут такого? Забавная цитата на эту тему:

I thought that this was a funny story about the Project Conference.

During Tuesday’s keynote by our GM, Mike showed off multi-level undo in Project. Our VP was sitting in the audience and heard the person next to him gasp and say "Oh My God …" The audience burst into applause after seeing Mike undo a bunch of actions.

We had demoed this same feature for some of our Office colleagues about a year ago. Mike overheard someone in the crowd say something like "what’s next? support for bold characters." There were some who had doubts whether we should stick it out and keep making a big investment in this feature when perhaps few people would really appreciate it.

Rolling back the clock to 2002, we held several advisory councils where attendees made Project support for multi-level undo a top request.

MLU (multi-level undo) has been a massive amount of work (between 2 – 3 developers for a couple of years). The complexity of being able to roll back results made by the scheduling engine is huge and not especially obvious.
 

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Dieter’s ProjBlog : Favorite Response to Project Confernce Demo