KDE SC 4.5, which was supposed to be released today, has been delayed by a week. A lot of changes were made after the third release candidate and the release team was not comfortable with releasing it without some more testing.
This is what the announcement in the kde mailing list says:
After discussing the amount of changes that have gone into the 4.5 branch post-RC3, the release team has decided to wait another couple of days for things to settle down and to re-tag the 4.5.0 release from branch in a bit more than an hour, at 1600 UTC. We'll push the further schedule for the 4.5 series for 1 week as well. The current plan for 4.6.x is not affected.
If no show-stopper bugs are found, KDE SC 4.5 will now be released on 10th August.
I have been using the release candidate and I have not found any critical bugs. However, the new blur effect does look awesome. Waiting one more week for a the final relase of KDE SC 4.5 should be worth it.