When Sony Ericsson explained how hard it is to release a major software update, we got the feeling that we're in for a pretty long wait. Yet, it seems that the company's developers are progressing faster than expected as they just released an alpha preview, which can be used by devs to start working on apps for Android Ice Cream Sandwich (ICS) right now.
The preview ROM isn't suited for a day-to-day use - major features like telephony, Wi-Fi and Google apps aren't functional just yet. Also, only the Xperia arc S, Xperia neo V and Xperia ray are getting ICS preview ROMs. The rest of the phones will still get ICS when its finalized, of course, but if you want to check out the alpha you need to use one of those three.
If you're a developer, who wants to flash their compatible phone (again, this really isn't suited for daily usage), you need to be running software with build number 4.0.2.A.0.42 (that's the latest available).
Also, you need to unlock the bootloader, but keep in mind that if you do that, some issues may arise when the proper release of the Ice Cream Sandwich starts seeding to your phone.
Anyway, there's a good deal of things that are already up and running and here goes the complete list:
You may want to check out the following video, showcasing these new things. Much like with the leaked Ice Cream Sandwich ROM for the Samsung Galaxy S II, the custom interface covers most of ICS but you get to see a glimpse of Android 4.0's cool new elements here and there.
If you like what you see and want to develop apps for ICS, you may want to follow this link to the Sony Ericsson's blog post for more info and download links.