I've been testing mine today. I've got mixed feelings.
First the positives: Overall the build quality and feel of the device and its controllers is very solid, even the single joy-cons feel useable with their wristband attachments attached. The screen in particular is gorgegous, with good viewing angles and a sharp image. The buttons feel good, except perhaps the "d-pad" but I'd have to test that on a 2D game. I also like the system software so far in terms of functionality and its look. Compared to the somewhat bulky and tame Wii U, the Switch definitely feels like a sleek, current gen hybrid device for a slightly older audience. This is helped in large part by the excellent branding.
That said, the system is plagued by small and bigger niggles. As reported, Zelda's framerate is definitely worse in docked mode, which to me is inexcusable as this difference should have been the opposite or, preferably, non-existent. The left joy-con has been acting up by desyncing pretty much constantly (while using the grip mostly), which is also inexcusable as it makes playing a game nearly impossible. I really, really hope both of these can be fixed with updates.
In addition, the very narrow single kickstand seems completely too small to keep the system stable and upright in tabletop mode when using it on any slightly moving surface like a tray table in a train or, yes, in a plane as advertised. Two kickstands would have been far better. I also still can't really believe that they chose to put the charging connector at the bottom so that it prevents charging while in tabletop mode (unless you buy the bigger stand...). Docking the system had me worried about scratching the screen because of a lack of soft material inside the dock, and today a thread popped up that confirmed my worries, meaning I'll have to apply a screen protector for the first time ever (since I never needed one before on any device save for the 3DS, which I solved by always using a piece of cloth when shutting the flap). This is a big problem I feel, one that should have been ironed out during product development. Finally, having no headphone jack on anything except the console itself sucks as well as I'd prefer playing on TV while using simple earbuds like on PS4 (now especially when our daughter is asleep in the other room). The pro controller at the very least should have offered this option.
In short, I'm happy with my system, in part because of Zelda (which I admittedly could have played on Wii U as well...) but also worried about quite a few design decisions and day 1 problems. Hopefully some of these will be fixed without too much hassle like recalls...others, I'll have to learn to live with unfortunately.