I figured I'd start out with a quote because one of the things I read about this film was that it would be all about the quotes, so I feel the need to oblige. There aren't a ton of great quotes in this film, but there are a few that stand out.
For those that want to cut to the chase, I'll bottom line it for you and you can decide whether or not to skip the rest of my review.
Bottom line: This is a "low expectations necessary" film. If you wanted to see snakes, a plane, and Samuel L. Jackson, then this is the movie you asked for. If you were looking for a complete, over-the-top bad film, this isn't that either. But this is what-you-see-is-what-you-get.
Contrary to some reports, this isn't a rip-roaringly bad film, fit for MSTing. It's a mediocre film with passable SPFX (and somewhat intentionally bad SPFX, like the snake-view-cam). But what the filmmakers are banking on is the audience knowing Samuel L. Jackson's reputation (and popular culture inflation) as a smooth badass character and their appreciation for him playing off that character.
If they had intended to make a really bad film, then they could have. There are plenty of horrible examples. But doing that well is actually more creative work than making a mediocre film.
The acting in this film is slightly above what you can expect from your average action flick. If you disagree with that, then you haven't watched enough action flicks and you don't know how bad the average is. Sam Jackson plays it pretty low key, not over the top. He's just your cool version of Samuel L. Jackson and he happens to be an FBI agent who ends up on a plane full of deadly snakes.
The plot is thin, and there are huge holes in it. Par for the course for average action films. The only place it really goes beyond mediocre is in the ridiculous situations the plane passengers get into specifically so that they can be bit in satisfyingly shocking ways. Other than those, you'll notice all the usual airplane movie clichés. You know, the kids flying alone. The baby on board.
That said, I had a good time. I saw it alone and it would definitely have been an improvement to see it among like-minded friends. But the audience obliged by reacting at the appropriate moments and cheering when SLJ delivered his money line, the one that was put in specifically at the request of "the internets." Sometimes a movie is a pop culture phenomenon. Sometimes that's pretty much all a movie is. (See "The Blair Witch Project")