Hi Nick,
My experience from four or so years ago is that the Canary Wharf area of Docklands is an up-and-coming area - new build flats for a reasonable price, etc. I flat-hunted out there, but ended up living around St. John's Wood/Swiss Cottage. Canary Wharf is mainly a commerce area. Things may be changing, but at the time, the area was a very quiet place in the evenings. It's buzzing during the day, but it turns into a ghost town once all the workers have left. If you're looking for activity right outside of your doorstep, you won't find it there. The DLR is as reliable as the rest of the Tube, in my opinion. The Jubilee line and the East London line provide reliable Underground access to the rest of the city.
You asked specifically about Wapping, Rotherhithe, Bermondsey. and Canada Water. These areas are recovering from years of neglect after the docks closed in the '60s-'80s and they have had reputations as rough areas. Things are changing, though, and I wouldn't rule it out without having a look first. They are more residential and have more activity than Canary Wharf. Southwark Park is located here. The Docklands article on Wikipedia is good for getting some perspective on the area.