I was about to upgrade my Arc (rooted, .42 FW) to ICS 4.0.4 as it sounds so lucrative, but I am very much discouraged after reading the pros & cons by users on the Sonymobile Blog. http://talk.sonymobile.com/thread/35431
Some definite cons i read are:
1. Laggy UI
2. Deteriorated camera experience
3. heating of device
4. fast battery drain
5. no update in music player
6. bad sound quality
7. HD games lagging and crashing
8. tonnes of bloatware
if its just for the user interface, i have a similar UI on arc which is the Xperia S Home apk from the BIG MOD Pack...
Please post your reviews on the new 4.0.4 ICS update
EDIT: with new ICS UPDATE, I Meant the STOCK 4.0.4 ICS Update recently released by Sony for Xperia 2011 devices, custom ICS ROMs are obviously very good as they come with tweaks applied.