Everyone seems to be looking forward in seeing Microsoft actually fail, or outperformed by a competitor. The Register now speculates that Xbox may not reach it’s target sales of 4.5 – 6 million units world wide by the end of June.
If they're right, then Xbox is probably confirming to the classic Microsoft consumer sales profile. The company is generally extremely good at hyping a product at the start, and getting retailers fired-up and stuffed with stock, but tends not to be able to sustain the momentum achieved over the first couple of weeks. When it comes to Windows, of course, this is easily masked by 'sales' obtained via the OEM franchise, which is most of them.