I'd been told by a friend that apparently Episode 10 was causing a lot of grief for people - that prompted me to go through Episodes 6-10 tonight.
Well...in all honesty - I don't understand what the big deal is. I'm going to be quite honest. Episode 10 is probably my favourite of the ten that have aired thus far. But not for the reasons most people are listing.
6 bored the daylights out of me. 7 and 8 were reasonable but incredibly camp, not that thrilling despite the action and Kotomine in F/Z is a complete buzzkill compared to what he is in FSN and why. If it wasn't for the banter between Caster and Saber/Lancer, those episodes would have been lax for me.
9 was one of the better episodes for me. Probably the first time all season I felt some proper connections to characters other than Saber and Irisviel. Something I'd been hoping for.
10 continued in that vein. And maybe that's one of the problems. For eight episodes, there's been little emotional attachment/interest to most characters in this show. Face it, a good deal of the people involved are cold and clinical in their methods - which isn't a bad thing in itself but the fact some of those characters are incredibly dull (namely Kiritsugu, Kirei and Tokiomi) just isn't doing much for the cause. Perhaps the fact we're suddenly being directed to care about some of the characters doesn't seem right to a significant proportion of those watching? Being able to be detached means you could watch the characters duke it out and feel little guilt in seeing what happens to them. Episodes like 10 bring some humanity and warmth to the mix, reminding you there are people involved here and that it probably is worth caring on some level.
As others have said, there is a need to create links to FSN from F/Z. So far what has been done seems to be accomplishing that. 10 seems an episode that would be appreciated more by those who have played the FSN game and understand what Rin became, but not so much for those starting their journey in the Fate universe with Zero. The purpose of the episode seems simple for me. Rin was once innocent and naive. The experiences she had in that episode taught her about the darker parts of life and what becoming a mage would involve her in. This episode filled the gaps for me and helped me appreciate who Rin is in FSN moreso.
Debates I've had with friends IRL have crossed the 'is it necessary to have played FSN to be able to watch F/Z?' Generally, no. Enough is apparent to watch it independetly/first. However, some scenes/moments won't make as much sense without having played FSN, particularly the Heavens Feel route. And that's going to be something those not as familiar with the Fate universe will have to put up with all the way. Tokiomi's reasons for his actions make more sense knowing FSN explanations, but there not necessary per se.
10 seems out of place to some perhaps since 6-8 were so intense and emotionally detached? Frankly I appreciate Rin's part in the saga to remind the viewer that there are people involved and that some of the major players in the Holy Grail War have been forced to harden their hearts in order to claim the prize. Frankly, 6 almost killed my interest in the series and 7-8 didn't help much. 9 and particularly 10 have revived my interest. And I think 11 will if that preview indicates what I think it did.
The themes behind the difference in ideals/goals for the Kiritsugu-Kotomine and Waver-Archibald feuds will hopefully appear in the near future. Although there's only 3 episodes left to the 3 month break in airing ufotable are taking to prepare for the 2nd half, so that may be a while. I seriously hope they do some justice to Kotomine soon, though. He was a darn good character in FSN but so far he's been pretty darn weak in F/Z.