I've heard quite a bit about this show before watching it and I must say, it lived up to my expectations. FSN is a dark thriller-action with elements of magic and a hint of romance. Overall, the show was a blast to watch and maintained a very high bar of quality throughout. Don't be surprised if you find yourself forgetting the time and continuously watching marathon style.
Animation:
First, I'll point out that the characters are well drawn. Unlike many other shows, the characters actually look relatively (not necessarily behave) mature rather than just cute. Granted, now with hindsight everything here is way childish compared to Fate/Zero. In addition, there are very many battles here in which effects are heavily used in a very effective fashion. Note that there is a considerable amount of blood. And yes there is indeed a character named Rin Tousaka who is just begging to be watched. That said, those who really like Tousaka should check out the newer Unlimited Blade Works retelling.
Sound:
The voice acting was well done, obviously I'm going to point out Kana Ueda for doing an awesome job as Rin- such a prime combination of cuteness and bite.
The music in general is superb. The first OP in particular is extremely memorable and fitting, with a hint of mystery. Kenji Kawai also did an absolutely brilliant job on the BGM, giving the show a very unique and atmosphere-rich feel.
Story:
I'll start with the negatives since there aren't very many. Don't expect heroes to coincide with what you know the heroes to be. They are only loosely based on historic figures and the anime takes its liberty to modify what it sees necessary (King Arthur = female??). Also, there are many intricacies such as the real identity of Archer that you may not get at first.
As for the actual plot sequence, it is superbly done. The viewer is kept waiting to find out who is Shiro's next opponent and then, once the plot plays out, rewards the watcher lavishly. Watching the uphill battle between the odd pair of Shiro and Saber (the weakest, pseudo-magician and the strongest servant) and the other masters was very intense. Throw in another magician (Rin) and her Archer servant and you have one awesome action adventure.
As an aside, there is also the question of a romantic development between Shiro and Sakura/Rin/Saber.
Character:
Shiro is a dynamic character. From the beginning, he seeks the idyllic dream of being a champion of justice. His only passion is to help and protect others, at whatever cost to himself. Others find this do-goody personality very annoying since he seems completely incorruptible. However, by the end, he is fighting for a completely different reason. Shiro and Saber begin as a master/servant relationship but after a few battles, it is apparent their relationship develops into something further than just that. I found this development to be very well executed; there's quite a bit of foreshadow if you look for it.
There's also Rin! She seems to be an amazingly talented magician yet it is obviously clear that she has some feelings for Shiro (and a perfect example of what tsundere should be). Overall, the development of the characters is done extremely well. You'll realize that even the villains will have some good points.
Value:
This show is not too long, and is very action-packed and plot-driven. It might start out a little slow but the overall show is very fast paced and will keep you on your toes. I re-watched it right after finishing to pick up on more subtleties. Definitely a classic, and a reference point by which to judge other action shows.
