The Ipad isn't quite as established as the ipod / google were when zune/bing were introduced. It's getting there, sure - but the surface really does make the ipad just look like an oversized ipod touch, it could disrupt the market.
You mean the Surface Pro, because the Surface RT... the one that´s actually able to compete with the Ipad in terms of price is in most ways vastly inferior to the Ipad (except for a yet to be detailed version of Office).
I´m not saying that these are bad machines, but i wouldn´t be expecting much of an impact outside of the enterprise market. The average consumer doesn´t want office productivity out of his/her tablet. They want a beautiful screen (Prime/Ipad Retina), they want a simple Operating system and above all... they want a stupid amount of apps they can throw money at.
Oh, and convenience, something a tablet with a hyperactive loud fan is not very good at.