I'm not sure about the D90, does it have the same 3" screen as the D300? If so, it allows you to zoom in to 400%. Two steps out from max zoom is 100% actual pixels view. I don't know how that equates to the Canon '10x', but I can't imagine wanting or needing more zoom than the Nikon LCD offers.
As for not getting full resolution from LiveView, that's nonsense. What they may have been thinking of is the fact that the LCD is actually composed of 900K 'dots', where each dot is red green or blue. That's equivalent to 330K RGB pixels. It's still the best LCD currently on the market though.