Erikku,
Tinnitus results can vary greatly for both radiosurgery and microsurgery. I was told by GK physicians that the goal of GK was to keep the patient from getting worse symptoms, but not to improve them. I was told by microsurgery physicians that tinnitus could go either way, but that many see improvement.
For me personally, I had tinnitus all the time prior to microsurgery that changed sounds and volume, worse when stressed and not as bad when relaxed. I had microsurgery just over 7 weeks ago and the constant tinnitus is completely gone. However, it was replaced by a low volume squeak in my AN ear either when I speak or have a louder sound coming in my non-AN ear. So, for me, the pre-surgical tinnitus was replaced by a much more tolerable form of tinnitus post-surgery. Actually, I don't hear my current tinnitus unless I try to pay attention to it.