It's an interesting concept, I think there's some room to experiment and improve though.
In terms of flow, the city/tree one and the city/highway one's are the best. They seem like more of a complete image. Although I know you're not going for a pano type thing, so that's not what I mean.
The bench one, like, it's just a bench. Not really a cool location, it's just strange looking the way the benches are, and the mirror thing isn't helping.. I think the images separately and together could have been better composition wise. Go back and look around.
The city one didn't look like the same spot mirrored until I looked closely, and you can follow the train tracks around the whole frame, which is nice. The timing of the train was good on both sides, and this ties the image together nicely. This would probably look nice as a large print. I like it, and I think it's probably the best of them.
The one with the skyline and the cars is probably the second best. I don't know about the tree though. It seems important and necessary with this effect, but it takes up a large amount of the frame and I feel like if you were even a few steps back it would have been nicer. It's right in the middle/in the way of where I want to look. Seeing the top/entire tree may have been beneficial, maybe even being able to see over it if possible. Time to break out the ladder.
The train one just looks disjointed. The light trails go all the way to the inside edge, but the train in daylight doesn't. I know you couldn't avoid the light trails coming in (or at least I don't think so) so you may have wanted to have the front of the train near the inside edge. I don't think your effect serves the image well here either. I'd assume you were going for the clashing angles, but I don't know, I don't think it works here.
Also, how are you compressing? In most of the night parts, you have some strange artifacts and gradations in the sky. The tree, in the city and train one with three trees in it, has some weirdness near it. And so does that electrical pole thing by the center of the night part.
Keep trying stuff though, good to see something different. Think about how this effect serves the image. Like I said, I think it helps some and doesn't help others. Maybe try different white balances or colors for the night. I don't know if it will remove the nightish feel, but try it. You could probably cut down on the orange a bit. But I'm a fan of cooler color balances, so that's just me.
I definitely liked the shots as a whole, and the series, the only thing I didn't really liek was the overlapping of the two pictures in the center. I just feel like it was just kind of distracting, and I think your whole series would've worked just as well without it. But as a whole, I really enjoyed it.