This is not the first delay, but it really was looking like SP2 was going to be with us this month. That's still on the cards, but don't hold your breath. Microsoft has NO intention of releasing the update until its very sure that its ready.
There are a number of new features coming in SP2. A "Security Center" will provide an overview of all system security settings. A better firewall (to challenge Zone Alarm) is also on the way. There are also many other updates, especially to internet browsing and e-mail capabilities.