I upgraded my phone to 12.1.A.1.205 right from 12.0.A.2.254 (I never took either 12.1.A.0.266 or 12.1.A.1.201, I stayed in 4.1.2), which was the firmware my phone had when I took it out of the box. Since 9 days I've been running on 4.3, and the experience is decent, although there are few bugs here and there. I don't know though if I want to go back to what I had (4.1.2) or stay with what I'm running now. A lot of people here on xda say that the 12.1.A.1.205 build fixed a lot of the bugs existed in the previous builds. Still, I'm on a dilemma. I'll post below the bugs I found so far:
-When the phone is turned off and charging, if I turn the screen on it'll show black screen. Even if I turn on the device (still in charge) it'll show black screen. If the screen turns off and I turn it back on though it's completely fine. (I can provide a video showing the problem is anyone wishes so)
-The backlight issue commonly found in 12.1.A.1.201 (noticed it only 4-5 times, I think it's now running fine)
Except these 2 bugs, my experience with 4.3 is good. The ram managment is actually much better than 12.1.A.1.201, which I'd tested on another xperia sp, and the overall perfomance and response is actually good. I don't know what to pick though. 4.1.2 or 4.3? I mainly use the phone for video streaming, listening to music and gaming (especially with ppsspp), but it's my daily driver. Apologies for the length of the post. An answer would be much appreciated.