ActiveSync 4.5 Released
Just 2 days ago, Microsoft Launched the latest version of ActiveSync, ActiveSync 4.5 which could be downloaded at http://www.microsoft.com/windowsmobile/activesync/activesync45.mspx
However, if you're using Vista, then this does not apply to you.
Honestly, I've no idea what's the difference, except the newer UI. =)
Read the complete post at http://darrensim.com/blogs/techbits/archive/2007/02/16/activesync-4-5-released.aspx