Both are consumer entertainment devices. Thats what the link is. The iPad was the fastest selling, now i guess it isn't. The same way that a DVD player and iPad aren't the same. But yet the iPad had a faster adoption rate
Except the analysis in the article is woefully poor.
The iPad was massively supply constrained for the first several months of its life and sold 2 million devices just about as quickly as they could be made. The Kiinect, while it's seen a little constraint for the stand alone units, is relatively easy to find.
The iPad was only available in the US for the first two months of its life and then expanded to a further 9 countries (there was an overlap of about five days I believe). The Kinect has had a much wider launch.
The iPad was going into a totally new market, the Kinect is selling into the established (and huge) gaming market with a user base of tens of millions of Xbox 360's availble.
There's a whole host of other issues too (the christmas market versus launching in April chief amongst them) but the first two are the key ones. Yes, you could argue they're both consumer devices but they're playing in such vastly different markets it's almost impossible to make a direct comparison. Frankly I'd say that Kinect only selling 2x the units of the iPad at launch with FAR better conditions to sell speaks volumes about just how well the iPad has done since launch rather than t'other way round.
On top of that of course there's another issue where the OP said 'the sleeping giant awakens to stomp on the competition' where, of course, the iPad and Kinect don't compete. At all. Well, outside of ludicrous Analyst rubbish like 'best selling gadget ev3r' of course.