It's the latest "official" from vzw. There have been a few leaks since. Check out the OS forum for everything OS related from the latest leaks, hybrids, and detailed installation instructions.
Posted from my CrackBerry at wapforums.crackberry.com
+1. If you are even semi-adventurous, then check out the Telus .419 OS. It resolves many of the problems with .328 (you can find out which in the Storm OS forum). I REALLY don't know why VZW doesn't just go ahead and release it.
419 is a really solid OS. I gained memory after upgrading, and it runs smoother than 328. OS 5.0.0.591 is also out there for Storm, but I have no experience with it.