I am 3 years out from Gamma Knife and have never looked back. I wasn't worried about first MRI but was also felt very relieved when it came back good. Had the 2nd MRI 1 year out and they told me they would call and get 3rd MRI at about 3 years. No problems to date. I flew to meetings day after GK and even got home the day of before my children got in from school.
Mine was 10-11 MM in size and hearing has remained the same as best I can tell. There was some slight "dizzyness" as tumor was swelling and dying but all that passed in the first 6 months post GK.