The title is a bit off - this isn't so much a blog of Mac app design as a blog of speculative Mac app UI concepts.

Some of them are quite nice in purely visual terms, but they tend to lack any rigorous UX thought. The Slack one is a perfect example: Yes, putting the channels, direct messages, and private groups into their own tabs looks neater, but now I would have to click twice instead of once each time I switched between the two channels I use most often.