I ran this last year. One of approximately 1,500 runners, although as they run a 10k(?) race on the same morning, there was quite a crowd at the start.
Starts and finishes at Sunderland's Stadium of Light, so facilities are excellent. Steve Cram is the Race Director so he should know a thing or too about racing!
The course is broadly three out and back loops (although not covering the same roads, if that makes sense) so it's a good one for spectators to see runners a few times. (My 'team' managed six sightings). It is relatively flat, with a few undulations. taking in some of the city centre, some of the seafront and through two of the parks (names escapes me).
From memory most, if not all of the course is closed to traffic, although padestrians did wonder along some of the footpaths near the end but nothing to bothersome.
Nice technical t-shirt, medal and free massage at the finish.
Easy to travel to on the Metro as there are stops five minutes walk from the start and finish.
I'd definitely do this one again if it wasn't for the fact I lived in Essex and it was a bit of a trek (I too had it as a back up for London)
hope this helps - happy to answer any other questions!