Another helpful fix would be to have the program not crash when deleting multiple contacts (say 15000). The error that occurs is along the lines of Act has stopped responding and has closed, click to report the problem.
Now, the delete process itself is already really slow without the crash, but having to restart ACT and find all the contacts to remove again is time consuming. Speed up the delete process by not refreshing the list view until the delete is completely finished, we don't need to see the contacts get removed from the list in real-time, it's a waste of resources and slows it down too much.
Same thing with updating records, we don;t need to see it refreshing, kill the main screen until the update is done, I bet we would get much better performance that way.