Lux Research posted an interesting grid that shows how different display developers rate on technical value and business execution. It includes mature technologies like OLED and electrophoretic and emerging technologies such as electrochromic and electrofluidic displays.
E Ink comes up on top in both technical value and business execution is E Ink - with high score in technology and IP and strong partnerships and management team. In face, E Ink is the only company that scores a "strong positive" - with their nearly 100% market share of the electrophoretic market - which is used in products such as Amazon's Kindle and B&N Nook e-readers.
Besides E Ink, OLED materials and equipment developers have a clear head start over other technologies, with notable players such as UDC, CDT, Novaled and Kateeva.