If you didn't like this movie (SPOILERS)...
Then it's whatever, not your cup of tea, it's cool. But to say that it's a bad movie because it ripped off Drive, or because it had a "jarring" tonal shift in the second half, or bad acting, come on guys. Those are the three biggest "I didn't like this movie" bandwagon stock responses I've ever seen.
I'll start by addressing the first point, which is that many people seem to believe they ripped off Drive with this movie. Well, in what way? Other than that they both have a mildly similar soundtrack, I'm really failing to see how this is the case. The movies have very different tones, different emotional cores, and completely different stories. The central figures in both stories (The Driver in Drive, and David in The Guest) are of two completely different walks of life and have entirely different personalities. Drive is set in a big, neon-lit city on any old day while The Guest is set in a small town around Halloween, decorations and all. And the stories, well, you can tell just by reading ths synopsies for both movies that they are nothing alike. Hell, I guess Ryan Gosling and Dan Stevens bear a slight (the slightest) resemblance to each other, but nothing else really. So I guess what it comes down to is that now, any time a movie has some 80s-style synth music in it, it's ripping off Drive, because you know, Nicolas Winding Refn was the first director that ever thought to do that.
On to the second issue of the "tonal shift" in the second half that apparently "jarred" so many. I mean, what about it was so out of left field for you? The action element, while increased beginning with the MP breach on the house that kicks off the second half, was already established. We saw David beat up the guys at the bar, and we saw him kill Craig and Higgins. The two scenes were pretty action-oriented, so for there to be more later on shouldn't have been that shocking. The Halloween element, and the maze particularly, was also already established, just increased in the second half. We see many shots of Halloween decorations throughout, there's a scene taking place at a Halloween party, and we see the brother character helping set the maze up a couple of times leading up to the final confrontation. So basically, the movie took two elements that were present from the beginning and developed them as the clock ran forward. Sounds like good filmmaking to me!
And third, the acting. It was fine. The actors were all believable in their roles, even Dan Stevens, who had the most difficult role to pull off. None of the acting is overly "flashy" or "scene-chewy" (even Stevens is more charismatic than flashy), but that doesn't mean it was wooden.
So again, I reiterate: I'm not criticizing anyone who disliked this movie. I loved it myself, but that's my opinion, and you have yours. But to anyone with the common complaints I've delved into above, I'm not quite understanding how those are valid reasons. If a movie was well-made and structured and everything but you still didn't care for it, it just wasn't your bag, well, just say that. Every movie has it's flaws (nothing is flawless), but there's no need to start pulling criticisms out of thin air.