Microsoft has just released Windows Server 2012 Release Candidate (RC) which can be downloaded from here.
For IIS, we have been feature complete since the Beta release so there are no new IIS features in RC since Beta. (Refer to this document for more details in IIS 8.0 features in Windows Server 2012.)
The RC for IIS has been all about the quality - from functional bug fixes, performance tuning, to reliability through stress. And we believe that we have accomplished, if not exceed, the RC quality. (Although the Beta quality has been quite impressive. We are running iis.net on IIS 8.0 beta and we have had successful GoLive events with several customers.)
Please take Windows Server 2012 RC for a test drive and let us know what you think.