In the sideboard, cut a Crypt and an Orb, then add 3 Hurkyl's Recall and 2 Surgical Extraction. Affinity will be a brutal matchup against this deck, as it's just too fast. The Extraction is for the decks where a little more control against combo is good, like Twin.

I was going to suggest cutting an orb or and a crypt as well, but I was planning on suggesting 2 Nevermore and 3 of either Divine Offering or Wear / Tear.

Hey wolfging, love the deck! I'm by no means an expert, but I have one or two quick thoughts:

1. You don't want to be rebounding Sphinx's Revelation with Narset Transcendent's -2: any in a mana cost when rebounded is automatically zero... However, rebounding a Supreme Verdict is pretty sweet. If you're in a situation where you need it, it's effectively a time walk (they won't be playing any creatures for a turn, and if their board presence is such that it requires a verdict, then they want to be playing creatures)
2. I would replace Think Twice with Serum Visions. Visions is cheaper mana wise and allows you to scry before you bump up Narset, helping you draw exactly what you wanted with her.
3. Have you considered Myth Realized? I know Abrupt Decay, etc. but for only one mana, it rewards you for just playing the game... I've only recently been toying with it mostly because it just naturally avoids your Supreme Verdicts. Maybe a one or two of? Even late game, it isn't a terrible draw, as you can use it as a mana sink when they inevitably don't play anything because they know you have counters until tomorrow. I'm not sure what it would replace, but it's a fun win con that can quickly get out of hand.
4. For extra board wipes, my vote would be for either a gold old fashioned Wrath of God or, if you have a lot of graveyard shenanigans running amok, consider Terminus as a one or two of?
5. I don't have a good suggestion now that my buddy Dig Through Time is gone, but it does look light on card draw...

Like I said, I'm no expert, so most of this is probably way off, but... I love the deck (and Narset)

Nice deck! I haven't built many modern decks, but this looks solid! Playtest was fun.

Nice deck! +1 from me.

Have you considered adding in 1-3 more lands? Most control decks I have found to like hitting loads of lands and 24 isn't usually enough. If it has been working out well for you then ignore this but I just thought I'd say.

+1 just for the DNS reference!

I love Azorius decks, and this one is pretty rad, so +1 from me! The only suggestions that I can give you are: Calciform Pools, which is a land that can actually be pumped with counters during dead times, and that can give you extra mana for your Sphinx's Revelation; Baneslayer Angel or Batterskull if you'd like to have something else that gives you life, or a possible alternative wincoin to your AEtherlings; and, as someone above me already said, Serum Visions over Think Twice. Probably you already did these considerations by yourself, since your deck seems really well built and you seem pretty aware of Magic universe. By the way, this is my version of UW Control, it'd be great if you tell me what you think about it: Lock & Stock.

What about Terminus?

How'd you get the misprint elspeth to show up?

Batterskull is a better win-con than AEtherling. AEtherling was good in standard because standard is slow, but Modern is not. This is a format where most decks expect to win by turn 4. If you're playing control then your goal is to stop that from happening. AEtherling is a dead drop until you're 8+ turns in usually, and even then it requires you completely tap out to play it. You'd be better off with Batterskull due to the life gain or even Delver of Secrets  ^Flip due to how early it comes out.

Also keep in mind that Narset doesn't really work with counter spells. She works with Path to Exile and Supreme Verdict which can be fun, but the amount of targets you have for Narset is very small. I would consider running 4x Serum Visions in place of Think Twice, visions will trigger much more powerfully with Narset. I'd probably drop Sphinx's Revelation to 2, since that will be a dead drop the first 5ish turns as well, and that'll give room for the 4th Serum Visions. Also, if you add black then you'd have access to cards like Inquisition of Kozilek, Thoughtseize, Esper Charm, Lingering Souls, etc. Those would all be amazing targets for Narset. Liliana of the Veil and Sorin become available at that point as well. Oh and I hear that Snapcaster Mage is pretty powerful ;)