Now, the release of the Ice Cream Sandwich source code isn't directly significant from a typical user's perspective; this is raw code, after all, and not something you could just install onto your phone as-is.
The real significance is two-fold:
First, this means the Ice Cream Sandwich software is now considered complete. That's obviously huge.
Second, this means manufacturers and third-party ROM developers can start working on prepping Ice Cream Sandwich to run on all sorts of Android phones and tablets. The source code was the one piece of puzzle they were missing up till now.
The next big question is when Google's ICS flagship Galaxy Nexus phone will arrive. With the Ice Cream Sandwich OS officially out in the wild, one would imagine its launch is right around the corner; numerous leaks and rumors, in fact, suggest the phone could appear as early as this Friday Google has an Android-related event scheduled for Wednesday, so it's possible we could learn more then.
Thanks: Wicked, CJM & danDroid