Back in December of '11, Sony [Ericsson] released an Android 4.0 alpha ROM for the Xperia Arc S, Neo V, and Ray. The Sony dev teams has now released an update to this ROM, bringing into its beta stages.
Since the previous release, Sony has made a number of improvements to the ROM, including an updated UI, improved lockscreen, activated GSM modem and FM radios, and a quick dialer.
Unfortunately, Google Apps are not available for this ROM, nor are Wi-Fi and Bluetooth connectivity, as they're both still waiting for approval before they can implemented into the product.
If you intend on flashing this ROM, however, you need to be aware that it's intended primarily for developer use, and there are still a lot of quirks. With that said, if you want to give it a shot, you must be running the latest Xperia software on your Arc S, Neo V, or Ray (4.0.2.A.0.42) and your device must be unlocked with the official Sony bootloader unlock tool.
For more information, including download and installation instruction, check out the Sony Developers' Blog.