I want this too. I saw a documentary about a dying man who took this option. They interviewed him about the decision, then after his death filmed medical students dissecting him (from a distance, it was discreet) and interviewed them about the experience. They were grateful for his gift, and incredibly respectful when speaking about him.
The thing is, the inside of a body looks nothing like the nice tidy diagrams. It's a mess in there! I'd like these kids to practise on dead me before they start cutting into live people.