Its worth starting by pointing out that your tolerance for This is the End will be greatly influenced by your general tolerance for the brand of American humour that many of it's stars made their names making. So think of Pineapple Express (which I liked) or Your Highness (which I didn't) and you know what you're dealing with. The question then shouldn't be about the type of humour, but if it's a good version of that type. And the answer is mixed - its certainly funny, and the gimmick of playing a heightened version of themselves as the Apocalypse comes is a good one, well mined. In fact most of the best gags come from them echoing wider criticisms of their own work, but there is also a slightly smug air to it - hey! that movies sucked but it still bought me this nice house! Wink!
That said I'm not sure the story would work otherwise, as you'd no real connection to the characters. Where The Worlds End was strongest when it played with the fear that these characters were in some way you, This is the End is strongest when it keeps you at a distance from the pampered movie stars you are watching, so what they are experiencing can be funny. If you find Male Rape being played for laughs funny, which apparently the film does. But, turn up for the bad taste gags, get the bad taste gags, I guess.
What does come through though is that the film was probably a lot of fun to make, and it's to the credit of it that is the case. Too often you watch the cast having fun when you're not with this sort of project, and there is just enough discipline and focus to keep it on track. Its plot is pretty telegraphed, and it's ending...indulgent...but it just about gets away with that, and as long as the jokes keep working - and they do, by and large - thats all fine.
In the end, I think I pretty much got what I was expecting - something that made me laugh, and made me wince, but was largely "fine". It's not a classic - it's not even a classic of it's own little genre - but it's entertaining and just fresh enough in it's setup to not feel too stuck in a rut. Worrying reports of a sequel in the works, though, which may need a lot more goodwill to get through.