Share your experience!
My phone's notification LED served its purpose on Gingerbread but now on ICS it doesn't blink on missed calls or messages even though it works perfectly with FB notifications. Bug in ICS? 
Solved! Go to Solution.
Okay! I think i found the solution myself!
Just went through an article from Sony blog and I found out that enabling ' Extended standby mode' will disable all notifications! And thats what happened in my case! Now I disabled the option and the notification LED is working!
Same problem faced by me too. 
Try to repair the Software it might help u , For me Notification light is working fine in ICS.
Mine also, but sometimes notification LED doesn't work.
Repairing using SUS didn't fix it. I think it's a bug in the ROM. Hope Sony would deal with it and release an update to fix the issue.