This would be a great addition to the nav. I can imagine having 3 modes of viewing submissions: "top" (the current default), "new", and "popular" (for >100 votes). I already switch back and forth between the default (or "top") view and the "new" view. This allows me to get a good mix of seeing what the HN algorithm thinks is interesting, as well as what interesting stuff the community is discovering out there on the web. I can see this being well augmented by a third view that presents what's popular to the HN community.
Of course, adding another nav element gets tricky. How many nav links do you need before you start culling or redesigning? FWIW, it seems that grouping nav into 2 sections might be useful. One section would be focused on sorting the stream (top, new, popular). The other section would be focused on filtering the stream (threads, comments, ask, jobs). "Submit" is more of an action than a filter or sort, and might be better positioned as a control outside of the nav.
Of course, adding another nav element gets tricky. How many nav links do you need before you start culling or redesigning? FWIW, it seems that grouping nav into 2 sections might be useful. One section would be focused on sorting the stream (top, new, popular). The other section would be focused on filtering the stream (threads, comments, ask, jobs). "Submit" is more of an action than a filter or sort, and might be better positioned as a control outside of the nav.