I just flew my 250DFC with v3.50 in some pretty high winds. It lifted off fine but the first gust that hit it triggered major cyclic oscillation. It took all my ability to get it back on the ground in one piece.
This heli has never had any cyclic oscillation using 80 80 30 gain 40. Reading unochen's release notes I decide to try lowering the D gains first. I dropped both to 10 and surprise surprise it was fine.
So I would suggest those that have cyclic D gain set to 30 or higher to lower this setting before you fly after flashing to v3.50.
Now for the rest of the flight details. Excellent!
The piro optimize is definitely improved. My 250 would always nose down slightly in a piro. Now I feel like I could piro all day, with very little input.
The tail is very different on stop. Much softer in both directions. I'm using 70 50 15 and still have both decels at 25. Firstly I increased the Tx gain from 28 to 32. Then I increased the decels to 40. This gave me a small grunt on fast piro stop and virtually the same in both directions. No bounce at all. As long as it holds as well now, as it used to, I'll be very happy.
The cyclic felt crisp and smooth. I'm using 30 for all the RC deadbands and really like the way it flew, even though it was a very blustery wind.
The heli was also very locked in the wind. Most times all I had to do was put in collective to keep the heli in one spot.
All up a much appreciated update. I recommend you upgrade, but watch out for the cyclic oscillation.