Extreme lag with Sony Ericsson WT19i after update to 4.0.4 I have updated my Sony Ericsson Live with Walkman to 4.0.4 from 2.3.4 and now the system lags horribly. I have to wait for a considerable time for an application to exit. Even the in built basic applications like phone and contacts take about 5-7 secs to load.

Has anyone faced a similar problem? What can I do that would cure my system of the lag?
Yes, Sony made the ICS upgrade a horrible experience which does slow down the handset and lag.

Two choices:


downgrade to Gingerbread 2.3.x
Try switching to custom ROM called LegacyXperia to use JellyBean.


The experience is more satisfying and smooth. For that to happen:


need adb, fastboot binaries 
if your bootloader can be unlocked, check Sony Warning if yes and proceed to do so, you will lose your data
you would need to backup your apps (there is other questions on this site about this topic!)
download the LegacyXperia ROM, extract boot.img from zip, flash it to bootloader
reboot and toggle volume keys to get into ClockworkMod Recovery
choose wipe data/cache
choose install from adb sideload, CWM will wait,
adb sideload name_of_zip_file, CWM will start loading and installing the ROM.
reboot and enjoy JellyBean.