Nothing inherently wrong with old tech (up to a point). Manufacturers now know the issues with plasma and LCD, and have found ways to improve them. For instance, today's plasmas don't have major burn-in problems, and thanks to LED backlighting, today's LCDs have better blacks. OLED is still in its infancy. We don't really know how good it will be, or what long-term issues it will have.
That's why this sort of thing is called the bleeding edge.