I'll spare you the marketing, here are the three links you may be most interested in.

The download link is here: http://www.microsoft.com/downloads/details.aspx?FamilyID=50b32685-4356-49cc-8b37-d9c9d4ea3f5b&displaylang=en

The release notes are here:

http://technet.microsoft.com/en-us/library/ff728620(EXCHG.141).aspx

MOST important – what's new:

http://technet.microsoft.com/en-us/library/ff459257(EXCHG.141).aspx

The cas role has improved even more, with numerous improvements, including the ability to federate with self signed certificates (that's not a typo), but read on….

I'd like to mention a few more things which I'm excited about:

The multitenancy support is awesome, so is the depreciation of isinteg allowing individual mailbox repairs, so is the installer installing the required dependencies, so is public folder client permission support being added to the ECP, being able to reset a single virtual directory from a cmdlet, faster owa, etc,etc.

Bit of a ramble but there you go. Have a read, get excited and if you were waiting for sp1 to deploy exchange 2010 you finally have it!