I am finding ArcMap runs slower, if you have written a script, which imports arcpy.
You may wish to write a script that can be operated in ArcMap, through the python window, or as a standalone python script. If so, you'll have to import arcpy. However, if you do this and run it in the python window, it will run slower.
I have put this code into my script and it runs much quicker:
try: arcpy except NameError: import arcpy
This is saving considerable time in our scripts in ArcMap now.
This may all change in SP2, but none the less...Tweet