I hate to say this, but Xbox360 is a console that, with its high failure ratio during the initial stages of their life cycle, generates the subjective (even objective) need of purchasing better, more reliable models. Apart from this, the improvement in equipment and quality (WiFi, better cooling system, less noisy), even design, makes me think that there´s a undetermined amount of old XBOX users replacing their old models, an amount higher than expected. That could explain some of the (relative) low software sales in those months of confortable HW sales leadership.
In my case, I´m just waiting to the appropiate XBOX bundle to take the new model. It has really better value for money than my old, fat, (too warm) 360. And a wireless adapter is not that cheap...
The question would be what percentage is due to replacements. What do you think?