The new set is spoiled here!
I have to say; the goal of setting up an Allies vs Eldrazi format is coming along nicely.
Small joke aside, the set is...a little troubling to me. The focus on Planeswalkers is understandable, given the story that this set is trying to tell, but I'm concerned about what the costs will be once this set hits the market. Planeswalkers are already the most expensive cards out of the gate from any set and Oath is about making Planeswalkers even more profitable than they already are. I suspect many of those rares will become quite valuable very soon and it's hard to get excited about spending more money when the current Standard format is one of the most expensive ever.
That said, the attempt to give colorless mana an identity of its own is a solid one: it seems to be clearly attempting the standalone thing, instead of supportive of other colors, especially blue and white.
One thing that's a big of a drag is how there is only one White Eldrazi and it took until Oath to get there. It'sindicative (for me) of how difficult it is for WotC to really understand the color pie philosophies and how they can be twisted. The Eldrazi eat all the other colors except the "good" one? Really?
The Surge mechanic should get a strong evaluation in Modern and Legacy, because those formats allow for spells that can be cast without mana payments. Crush of Tentacles for five mana is incredibly good and with a card like Gitaxian Probe to ensure you won't hit countermagic, I think there's something pretty cool there.
So it's a real shame that they kept it to just red and blue: I feel like they should've expanded this to the other colors because the concept is just so interesting. Not just because of the applications in eternal formats, but also because of the possibilities for team formats.
In comparison, Cohort is really just Outlast with a terrible twist.
Support is the way that they're attempting to get Oathwatch and themes from Khans block to mesh, and that's fine. Nothing special yet but worth keeping in mind when looking at interactions in Standard or with other counters. (I want my -1 counters to come back, damnit! Let's gooooo, Shadowmoor!)
Other things I'm noting:
Small equipment subtheme: Weapons Trainer, Bone Saw, Stone Haven Outfitter, Kazuul's Toll Collector (as examples) suggest to me that there might be an equipment theme in the next block, which would make sense as the first Innistrad block had an equipment subtheme too.
Really solid uncommons: Warping Wail is the standout but believe me, there are some really good cards in this slot that I think will be workhorses for deckbuilders.
Colorless matters: reinforced in this set, naturally but suggesting that color matters might be relevant in the next block. I haven't seen that as a strong theme in a little while (there was an undercurrent in Khans) so it's certainly due.
Story truncation: I can tell that they were still planning on a third block because the storyline just feels shortened. Also, the story boring because it doesn't appear to have a consequence. The planeswalkers all seem to be alive and the biggest bad, Emrakul, makes no appearance. Well la-dee-da, man. Jace has been searching for help to fight the Eldrazi since Zendikar came out in 2009. What was all the buildup for, unless something is going to legitimately change?
That's it. I look forward to more Sealed matches with this block but I'm not seeing a lot of awesome Constructed possibilities here, just extensions, really. That's OK, I suppose but if Oath finally shook up the Standard format so it became a bit cheaper, that would really be good.