What about gamma ray bursts? I've read that our position more at the outer rim of the galaxy is beneficial because there are fewer gamma ray bursts compared to more dense regions.
On the other hand you are of course right - in a galaxy that is still undergoing intense star formation it is still dangerous to live in a dense region where a nearby young cluster can still render your home planet sterile through a GRB. However, our own Galaxy doesn't seem to be forming stars that actively anymore, and the chance of a new GRB pointing directly at a given star cluster is negligible.
Also, we're not actually within the outer rim of the galaxy: http://www.nasa.gov/mission_pages/sunearth/news/gallery/gala...