I found the ICS to be light years better than the gingerbread.
Before the update, Z operation is sluggish and unresponsive. Dual core Z perform worse than my single core ICS xperia ray android phone.
It almost made me feel embarrassed to use Z in the public. "Who is that poor sucker with that bulky and outdated thing!!"
After the update, everything is smooth and responsive. Almost no lagging in the music library and W menu pops up much faster too. The default video player can finally play .avi file.
The biggest surprise is probably the OTG playlist that Sony has finally incorporated for the players without sonic stage.
There are still some small issues like search function needed to be improved but overall I am very happy with this update.
I could not live your life.