If you find that with a relatively medium to large sized task list when creating new task or editing them takes many seconds to update the screen you may want to check the Settings->Appearance->Number of Lines shown option. 

Informant performs the best when you leave the Number of Lines option set to 1. When you set it to other options, Informant is required to calculate each row height when displaying tasks. This can cause severe performance degradation with large task lists.