Have only looked at the first page (will read the rest later) but having my hands full with a XNA project I'd say that absolutely the most important part of an "engine" is the object storage, allocation and display management. Using shader A or experimenting with render option B is definitely peanuts compared to this whereas gamers are most interested if the game has AA or uses SMx or whatever end-of-the-line graphical feature.Thanks again Roderic.