K2 recently released an update to the 4.5 platform. Apart from fixes, This update improves the installation experience and provides some nice interfaces for Sharepoint integration. I just installed it on a distributed (Kerberos) environment and it went very smooth.
There’s a New K2 for SharePoint Configuration Wizard embeded into Central Admin which gives you much more clarity as to what integration bits from K2 are being deployed and the status. It checks and guides through the deployment.
There is also another good addition to the Silverlight process designer for SharePoint. It now includes the Call Sub Process Wizard.
You can get it from here – http://help.k2.com/en/KB001110.aspx