I'm of two minds on the 8xxx issue. On one hand, he has a point in that
SL, despite not looking as nice as the newest games, requires more power to render due to it's streaming nature, and user created content.
Videogame companies generally only hire professionals, who design graphics optimized for the game experience. Often, if you never see the other side of a wall, there is nothing on the other side of that wall, not even the other side of that wall! Polygons are cut wherever possible, and scenes designed to look good within what the player's camera will show. Even what you see is carefully designed to look the best in as few polygons as they can manage. Texture maps are generally much lower res than the average
SL texture. Lighting is also carefully managed. Every aspect is made to run well, while looking good.
Ever download user created maps for games, and where the game itself will run perfectly fine with a high framerate, the mod community map runs at like half the framerate?
SL is like that, but even worse, since everything is made by the community, and there is far less control over the end user's experience.
On the other hand, RealXtend seems to do shadows without a big performance hit, or requiring an 8xxx nVidia card. Just sayin'.