Yes, lots more aerial imagery available in Potlatch 2. BUT, please dont rely on aerial imagery: much of the Bing imagery is sourced from GetMapping and is upto 10 years old: I’ve recently been working on Oakham and it does not show the Oakham ringroad (mostly opened by 2007). No aerial imagery shows the new A52/A46 roundabout at Bingham (http://osm.org/go/eu8w9gsq), nor do most commercial on-line map providers, but OSM DOES. This is because someone has gone out and surveyed it.

To add bridges, tunnels, changes in speed-limit etc., cut the way at appropriate points and add the additional tags to the new section of the way. Don’t worry about a way being chopped into lots of little pieces: it’s just the way OSM works.