It's hard to see this being a major success, outside of the (aging, shrinking) Nintendo hardcore. The consensus on gaming sites (and their forums) seems to reinforce this. So do the markets; Nintendo's stocks have fallen around 5.75% since the reveal.
The stock price shift will almost certainly have been driven by the price. It's higher than expected by at least $50 (and realistically closer to $100). Sony and MS got away with even higher prices when they were launching the PS4 and XB1, for sure. However, those consoles were significantly more powerful than their predecessors. They also launched at the same time as each other. So in essence, there were two expensive consoles without many games in direct competition with each other, which actually negated those disadvantages a bit. Nintendo are launching a less powerful console against two cheaper and well-entrenched mid-cycle consoles with extensive games libraries. That's going to be tough.
The launch games line-up is also poor. Zelda looks pretty good, but there is a cheaper Wii-U version also available that doesn't look appreciably worse. The rest of the launch window looks pretty pants. The XB1 and the PS4 had the same problem, of course, but again, their near-simultaneous launch actually offset that as a problem.
Beyond the launch-window, the games lineup is nothing special. The same first party range that didn't do much to help the Wii-U. A couple of more interesting (but still niche) second party titles like Xenoblade 2. Third party support from a few companies with a long-standing relationship with the Nintendo DS line (like Atlus), whose games aren't yet even confirmed for release outside of Japan. And a tentative dip of a toe in the water from EA. The poor specs, eccentric hardware and unusual control configurations are going to put a lot of other third party developers off.
I think the console itself is also going to be very hard to market. It's not quite clear what the USP here is. The thing looks large and clunky by handheld standards; more awkward than a tablet or even a PS Vita. As a home console, it's badly underpowered compared to the competition. Nobody has quite explained yet why the hybrid configuration is such a good thing, and the attempts to date to do so have been toe-curling.
On the plus side, it's region-free. That's actually pretty huge news and is a sign that even the most authoritarian of the platform owners is now being forced to open up a little. I might actually buy one just to reward that, because the fear is that if the Switch fails horribly (as I fear it might), then Nintendo will swing back to region locking in future. But it is really hard right now to see a pathway to this thing being a success.