I have a Deck, and I like what it does for me. But I'm well aware that the Deck is not a Switch killer. To start with, Nintendo has (IMO) an absolutely unmatched level of experience with handhelds. And they pretty obviously applied that to the Switch in full measure.

Secondly, the market for the two are (again, IMO) entirely different. The Switch is aimed at people who want to enjoy the newest iteration of Nintendo's continuing dominance in the handheld market. And for all that the Deck can emulate Switch games, it's customer base is pretty obviously gamers who want a lightweight (in terms of hardware capability), portable gaming PC.

To think that Valve (no matter how good their device is) can just roll in, boot Nintendo in the ass, and take over is wishful thinking.