I started watching this for the sole reason that Sugita Tomokazu was in it. I had no expectations, and had never even heard of the title. My first impression was "oh, this is just going to be a cheap rip-off of Death Note where they're going to try to shove as much mediocre bs into 1 hour as possible." However, I found myself inexplicably wanting more after it had finished (for two reasons, mostly good) I haven't watched Death Note in a while, but as someone who truly loved the anime/manga and is revolted by the idea of a cheap imitation, I can reasonably say that this anime did not sound the alarms, despite the noticeable similarities in art and music.
Unfortunately for this anime, it's just too hard to pack a strong plot line into two episodes, however, this OVA did a surprisingly good job at conveying a captivating but not excessively complicated plot in only 1 hour. In terms of mystery/detective stories, I can't say that the plot is very unique - undercover agents trying to expose a malevolent drug-dealing organization - but it is executed nicely with a clean few plot twists that are not too contrived or predictable. I can actually say that the execution of the plot is quite perfect, it's simple enough to be conveyed in one hour, yet complex enough to keep you interested and captivated. The producers made the (right) decision to end the show with a little bit of mystery rather than trying to explain everything in the last few minutes, which, while it does leave me a little unfulfilled, it also leaves me satisfied with the developments the story has taken.
While I was expecting it to be a rip-off of Death Note, but was pleasantly surprised to find that the plot did a pretty good job at staying independent. There are certainly similarities (to be expected of the shared genre) and there are some attempts to mimic the dark, tragic, and mind-game aspects of Death Note, but Switch manages to hold it's own fairly well in this regard. My only complaint is that is seemed to make a subtle hint at the supernatural in the end, but I may have been mistaken. If it ends up being true (in the manga) I'll probably be disappointed (Death Note only got away with the supernatural aspect because of how well it was explained and incorporated into the series) The ending is slightly unsatisfactory in that it leaves many loose ends, but I prefer that to them being hastily and messily tied together like too many other short (and long) shows do. I rather like the feeling of mystery it leaves us at the end, and it's actually making me want to read the manga.
The art/colors/animation/composition is definitely reminiscent to that of Death Note, without a doubt. However, despite my cringing at the clear similarities (and my fear that one of my favored series might be tainted by a crude copycat) I grew to really appreciate the quality of the art and the attention to detail. They may have imitated the art style, but they did it well, and if I had never watched Death Note I know I would definitely say that the art and animation is excellent, so I've given it a 10.
The OP is pretty good, I'm rather picky when it comes to music, but I can say that I did like it within reason. The ED (which you only hear once) is also pretty nice. As a 2 episode OVA I can't say that they really matter much, as you only hear them twice at most. My biggest beef is with the OST. Another noticeable similarity to Death Note is the heavily orchestrated soundtrack. I have to say that Switch did not to such a great job at incorporating this type of music into the show. While the music was good, there were times when it stood out too much and it was clear that they were trying to capture the same classical dramaticims that Death Note was so flawlessly able to do. Unfortunately, operatic an Orchestral music is very refined and possessed great potential, likewise, it is must be used carefully and be specifically tailored to the situation. There were certainly good parts, but I would have been more satisfied if the producers tried a little harder to find something that would work better for them. I like the idea of using orchestral music in a modern-drama-mystery-suspense, (especially compared to some other types of music) but the execution could have been better, though it was by no means bad, and in some parts quite enjoyable.
The Seiyuus on the other hand were very good, I really don't have any complaints in that regard. The Seiyuu lineup is actually pretty impressive.
It's pretty hard to develop a character in just 1 hour, but there is a shade of character development, if you're careful enough to catch it. In one hour we still have much to learn about the characters, much less give them room to develop, but we do have some clever plot-twists that shed new light on our main characters at different points in the show. I thought the characters were very well made, they all seem quite realistic, and even the "bad guy" is pretty likable (I can't stand it when the "bad guy" is pinned as evil and given an unrealistically horrible personality) None of the characters are too contrived, though they aren't particularly unique as far as anime characters go - but that is also part of their success. Nothing is over-the-top, the characters are relatable, intelligent, and well-designed (you can actually tell the characters apart!) and they all act like real human beings (which is sometimes rare in anime)
Overall, I really did enjoy this show, and it's short enough that I'd probably watch it again. It's by no means perfect, but I'm very impressed by the work put into it. I don't view it as so much of a series in and of itself (it's not) but as more of an introduction to the characters, story, and ideas that I will probably follow up on by reading the Manga. When I look at it that way, it's an excellent piece.
Perhaps my rating of 9 is a little generous, but in terms of enjoyment (or perhaps it was just surprise) I give it a 9, and I definitely suggest you give it a try. Make it past the (slightly cliche'd) intro and OP, and try not to get too cynical about the similarities it has with Death Note. Just keep an open mind and enjoy the show :)