Great episode! I am more than pleased by the outcome that the episode achieved.
My speculations on Archer were right--he has acted as a Guardian who has repeatedly been summoned to aid humanity throughout different eras, only having been met with disappointment after disappointment, which has during his cycle turned him into the cynical individual that he is. This is a prominent feature that I've been waiting for to reveal in some fashion, and I am pleased that it ended up being as I envisioned it. Archer is quite a model byronic hero, and I value stories that properly delve into what exactly has made the person so disillusioned from society, which the show managed to portray quite effectively. It is of course made ever so stronger with how it ties to Shirou, and how it reflects that despite his stark views on his ideals, even he can be broken to such an extent. Truly enjoyed that Archer called out on Shirou's stubbornness and how he brought forward that simply thinking that it will get better if Shirou believes in himself will make things go as he wants, was great. In addition that Saber / Rin was just glorious!
Speaking of which, I'm also very pleased by Saber and how it came around. For a character that has a relatively minor role in the story, it is always an appreciated quality that she isn't simply sidelined completely, aside from fight sequences. She isn't that much of a character, and having Archer remark (more pointedly this time around) upon Saber's own wish and where she actually stands, is a welcome aspect for sure. Shirou earlier directly asked her what she is fighting for, to which she naturally dismissed, and having in this episode seeing a glimpse upon her character is vital to shape her and simply out right characterize her within the context of the story. Having the ever so iconic glimpse upon the battle of Camlann visible--visualizing her struggles that she fought for--and establishing Saber's chivalrous nature, was something that pleased me greatly since I was afraid these qualities would be dismissed entirely.
Unlimited Blade Works had a solid build up, but was cut short way too quickly. Archer's chant and the utilization of visuals along with the tone of the music made for a very hectic scenario, and for me it was a joy to see it in full splendor... to a point at least. It was nice to see the revelation of what that place is, and I really had a "you guys are f*cked" feeling during that scene, especially how menacing Archer'stone was (great work from the VA there). This is also one of those scenarios where one can call a narrative ass pull regarding Shirou's role in the marble, but considering how the story has established him as a capable "projectionist", and how Shirou reflected upon knowing the workings of the marble, it works within the context of what the anime has established. Though really, why did Ufotable cut that scene instantaneously like that? I couldn't help but think that the studio suddenly went like "errrr guys, you know that awesome Archer scene? Well it turns out we spent our budget on that Lancer fight earlier, so we're gonna have to cut it short here". Not disappointed, but I was expecting a bit more, considering that the anime's name is frikking UBW!
Rin's dialog with Archer was striking, and she knows what to say and put forward, just as I expected she would. That's mah gurl! 
Also dat Gil / Archer face off!!! I couldn't help but smirk like a goofball, in how they just coldly stared at each other. I don't think they will clash, since I expect events to turn out differently than I'd expect, but boy would I love to see it.
All in all, plot wise some solid moments, but I feel Ufotable cut their budget a bit short on this particular episode, for some reason.