Along with the new branding, IntelliJ IDEA 15.0.2 has been shipped (inadvertently) with a number of bugs. To get help with the latter part (including the problem with freezing drag-and-drop dialog), download the latest 15.0.3 EAP build we just published. Ah yes, among these changes it also includes the Kotlin plugin Beta 3.
Your bug reports are vey welcome in the issue tracker.
Develop with Pleasure!