Jro45,
When you say file, did you really mean file, or hone with a stone. It's common practice to polish the sear with a fine stone to help eliminate creap, and it will also lighten the trigger pull a little too. Polishing the sear is generally done with a jig so as to maintain the proper angles. Changing the lenght of the sear by filling it could result in an unsafe gun.
Do me a favor and do one little test. With the gun unloaded, rack the slide to cock the hammer, put the thumb safety on, pull the trigger hard (did you feel it move at all, it shouldn't) then take the thumb safety off. Did the hammer fall? If it did, the gun is unsafe. Any time you do work on the hammer or sear, you should do this test.