Exchange Server 2013 Cumulative Update 1 (CU1) now available.

Yes, Microsoft has released Cumulative Update 1 for Exchange Server 2013.

Here are some important links to articles that you should first read before you start the installation or update:

Microsoft Technet: 
Exchange 2013 System Requirements

From The Exchange Team Blog:
Released:Exchange Server 2013 RTM Cumulative Update 1

Scott Schnoll's weblog:

High AvailabilityChanges in Exchange Server 2013 Cumulative Update 1

• Witness Server Warning Message When Using Certain Database Availability Group Tasks
• Self-recovery Behaviors
• Autoreseed
• Update-MailboxDatabaseCopy
• Set-DatabaseAvailabilityGroup
• Managed Availability: Get-ServerHealth and Get-HealthReport
• Best Copy and Server Selection Changes

Microsoft Technet:
Release Notes for Exchange 2013

Microsoft Download Center:
Download Cumulative update 1 for Exchange Server 2013(KB2816900)