Thirded. I do, however, have a lot of sympathy for the devs because while Manuscripts looks admirably simple from the user's point of view, it's actually a very ambitious piece of software with a huge range of functionality.
The current plans for collaborative editing are a huge endeavour and probably taking a lot of time and resources to implement. However, I still would have preferred to have a more reliable and bug-free version of the current functionality than more features; I reported bugs in the first versions that still aren't fixed.
It's very frustrating because the actual experience of writing in Manuscripts is far more enjoyable and productive for me than either Word or Scrivener, and I would really like it to succeed and continue development - especially given that the majority of alternative modern text editors are focussed on Markdown and are pretty useless for actual scientific writing (e.g. no support for tables, images, etc).
Anyway, I'd attribute the silence between the last few updates to the vast amount of work that mz2 has to implement the collaborative features; and to be fair, in the current environment, an application lives or dies by its ability to interoperate with others. Looking forward to the next update.