I did save my defaults as a stream, naming it Unread Content, and it did not save my preferences.
According to usability principles, default views should be set according to the most often used view or view of highest utility to the most users.
Surely, when looking for new content, one would rather be taken to the first unread content in a topic rather than the top of the thread. If the first post is unread, "first unread content" would embrace that use case as well.
As it is set now, the default view may be logical but not of high utility. This thinking occurs elsewhere in 4.x, such as in Reports, where the default view shows ALL reports, where most likely the mods would want to see open reports only. (In the case of Reports, there is no way at all to set preferences so they are persistent; every time a mod views that list, the preference must be set anew. See Reports need more streamlining
Don't show completed reports in main overview
Manage Followed Content is another example, with a default on invisioncommunity.com to Downloads. How many users are following Downloads? Wouldn't most be following topics in Forums?
Like Activity Streams, Managed Followed Content (and Reports) surfaces the database structure with an overwhelming amount of information, with tools of varying quality allowing the user to customize his or her own view. This requires extra steps from the user, who most likely wants one particular view (commonly an 80% preference) and may not have the patience or sophistication to fine-tune a view. I call this "designing from the database" instead of "designing for the user."
On one hand, there is design consistency in 4.x -- "designing from the database." Design consistency is desirable to some extent in UX. But when it comes to default views, usability design holds they should be governed by ease of use and utility to the user rather than logical consistency.