Importing 2,200 songs into Banshee took 97 seconds before if you had the four predefined smart playlists active. Three of those four look for favorites, so they don't match newly imported songs at all. If you change them from Rating > 3 to Rating < 3, they will match all the new songs, and importing is impossibly slow.
I just committed rate limiting for the smart playlists; if more than a certain number of update events come in per second it ignores them and refreshes everything when the rate decreases. Importing now takes 55 seconds for both cases - one second more than if you have no smart playlists.