We were spending a lot of time in each view_diff rebuilding the diffs.  Except for variations due to collapsing and syntax hilighting, these won't actually change.  Rendering these to strings and caching the results has resulted in my profile being mostly inside view_diff to being mostly inside django internals and locmem caching code.  Whoopee.

Looked at both collapsed and expanded versions of the diff.  Reloaded a bunch and looked at the profile data.