Software Sources works correctly, but a couple of the choices made could be improved upon:
[*] Sane organisation of countries in Mirror list - Canada and Australia are right near the bottom despite presumably being some of the more likely places that someone would be using Linux Mint in English from. For newer users this means that its unlikely that they will choose the right mirror if they do not wait (and yet there is nothing to suggest waiting is expected).
[*] ...and in regards to that, a progress indicator of some kind would be a good idea. Especially with the size of the Ubuntu mirrors list. As an experienced user I just used the same server as for the Mint mirror, but waiting for my local (Australia) mirrors to reach the top currently takes minutes, with no indication that I should wait and not choose the horrendously slow mirrors that "look" fast until a comparative server pops up. (The difference is 60-300kbps throughput for an overseas mirror, versus several Mbps for local mirrors - this is a big difference, and could affect perceptions of Mint updates, and the likelyhood a user will keep their system upto date [someone may choose to update rarely or give up on it - if they take too long]). For a new user they are unlikely to choose the right mirror.
[*] This last point is more of an "it'd be nice" - an indication of speed would be a nice addition to the listing (Relative speed indicators should still likely be kept). Relative speed alone is of little help, except for identifying the top one.
Hopefully a few others feel the same, or at least empathise with the mirror organisation situation (which is the largest part of the problem).
Note: Ive jumped up from LM14 so I dont know if the new software sources is new with LM16 (my assumption), or was part of LM15. I apologise if this was discussed post-LM15 if the latter is the case.