I'm quite excited for
Keeper of the Accord - ramp (and token production) in white is much appreciated. If the stars are aligned, you can potentially get lands on every opponents' turn, which is... sort of absurd. Alternatively, sacrifice them all to
Claws of Gix or another sac outlet and recur a giant pile of lands with
Planar Birth? Throw in a bunch of expendable tokens (not entirely unlike
Ophiomancer) and you get a very nice package.
I don't have a particularly strong opinion re:
Halana, Kessig Ranger and
Alena, Kessig Trapper yet. Halana provides repeatable removal / fight effects for green (since green traditionally lacks good creature removal), while Alena provides repeatable mana production for red (which, again, red traditionally lacks). Both look reasonable, but don't know how good they will be in practice.
Sengir looks... fine, but not amazing. That said, Partner is an extremely powerful mechanic, so will at least be very good in limited.
The Prismatic Piper is obviously not great outside limited, but it's an interesting way to make sure that everyone is guaranteed a legal deck.
Completing the land cycle is very much appreciated. I wish they had started with enemy lands, but better late than never. Hopefully these will end up being more affordable than the allied ones (or that the allied ones get reprinted), but I suppose we'll need to wait and see.
...sadly, may be difficult to actually play in person, but I'll try to get to a draft if I'm able to. Dedicated legend slots in Dominaria were a lot of fun, so glad to see it returning here.