As a pundit, Nate is left-leaning but I trust his impartiality when it comes to polling and statistics. That is ominous. He was spot on with his commentary on the RNC and DNC bounces as well.
From my perspective after watching the debate, I didn't see a bloodbath. Clinton's performance was solid and polished and, in terms of the debate itself and devoid of the context of the wider presidential race, she did win. But I thought Trump managed to stay on message, obviously not to the extent of his recent rallies with the aid of a teleprompter, but it was much better than his unscripted efforts earlier in his campaign. He also appeared restrained and thoughtful in his answers (by Trump's standards), which would have fulfilled one of his main goals to appear presidential, given Hillary's campaign until now has focused on his alleged lack of fitness for office. I assume the strong anti-Trump reaction is because, as james Dean pointed out earlier, a lot of people haven't really seen Trump in action until now. So it will be interesting to see whether that holds true for a meaningful section of the American audience - if so, then a lot of the pre-debate punditry discussions about how Trump and Hillary are being graded on different criteria may have been inaccurate. In fact, Trump may have always been headed for a post-debate poll drop, given his delivery style and lack of debating experience, if some viewers were going to judge him purely on his debate performance.
People have noted that Trump was defensive throughout much of the debate. A lot of that had to do with the questions asked though - here is a compiled list:
http://www.informationliberation.com/?id=55558. (Ignore the wider article which is biased towards Trump, but they did put together the list of questions which I am yet to find on other websites.) Most of them focused on Trump's fitness for office, rather than policy differences or any of the scandals surrounding Hillary, which have made her one of the least popular candidates in US history. I thought Trump handled the questions reasonably well, some better than others, but it gave him the chance to at least answer to some of the assertions made by the Clinton campaign and frankly quite partisan "fact checkers". Again, though, that analysis relies on the audience viewing the debate in the context of the wider presidential campaign and therefore having previously been exposed to these anti-Trump arguments.
That said, all of what I said above is opinion. Much has been made about this presidential campaign being different to others, but the statistics are always the most objective and reliable measure and they don't look good for Trump at this point.
TL;DR - Hillary won the debate in isolation but, in the context of the wider presidential campaign, Trump achieved what he needed to achieve. The question is whether American voters viewed the debate through the prism of that context. Statistics from previous debates suggest that a meaningful number of people will form their views solely on the debate itself, in which case the pundits and Trump campaign may have been incorrect in their view that Trump simply needed to appear presidential on the debate stage to maintain momentum in the polls.