[Toadling]

A couple other things you can try to improve performance:

1) Hide things you don't need. OmniFocus's performance seems directly related to the number of visible nodes. So put things "On Hold", collapsed sections you don't need to see, focus on particular folders, etc. Fortunately, OF has lots of options for controlling viewable data.

2) Don't leave the Library item in the sidebar selected (or no items selected). This causes the entire database to be rendered in the content area, which can be slow if you've got a lot of things in there. Instead, select a project or folder, then quit the app so OF will preserve that window state.

3) I personally really like this hidden default. It makes OF behave like many other OS X apps in that when nothing is selected in the sidebar, nothing gets displayed in the content area (rather than the entire Library being displayed). With nothing displayed in the content area, launching the app and switching between planning and context mode is very fast.

defaults write com.omnigroup.OmniFocus LeaveEmptySelectionEmpty -bool YES