I've written a long, thorough, mixed review of Kubuntu 15.04 Vivid Vervet 64-bit edition with the Plasma desktop, covering live session, installation in a multi-boot setup with Windows 8, 10 and several Linux distributions on a laptop with UEFI, GPT and Secure Boot, including look & feel, partitioning, slideshow, package management & updates, default and extra applications, multimedia support - Flash, MP3, HD video, desktop effects, smartphone support, hardware compatibility, webcam, suspend & resume, resource usage, performance, printing, battery life, overall impression, tons of small and large bugs and issues, and more. Enjoy.