Its definitely been serviceable. I really like it against stuff like Burn and CoCo. The real reason its in there is to protect my hand from Thoughtseize/Inquisition of Kozilek early on. Its also good against the mirror when you get into counter wars.

What match-ups do you bring in Rest in Peace? Other than super obvious ones like Living End and Dredge?

RIP will come in against Dredge, Living End, Storm, Gifts, and other graveyard based combos. I'll also use it against some Junk decks that run stuff like Eternal Witness, Scavenging Ooze, Voice of Resurgence, Kitchen Finks, etc.

As long as you are on Kiki-Resto, 1-2 Cascade Bluffs could be good.

Honestly, I think I'd rather have Sulfur Falls over Cascade Bluffs. So far I haven't had too many mana problems, but if I do I may go for Falls. I just don't like the fact that they aren't fetch-able.

Kiki-Jiki, Mirror Breaker + Restoration Angel ?

I was running that combo, but the casting cost for Kiki is rough in a 3 color deck, and the combo is a full turn slower than Twin/Exarch.

Restoration Angel + Wall of Omens gives you card advantage and resto angel is a pretty nice flyer that can makes attacks hard for your opponent if they don't want to get blown out by resto angel. Kiki-Jiki, Mirror Breaker + Restoration Angel works around Spellskite. Resto angel is a real powerhouse in these type of decks.

Cascade Bluffs is a way to fix your mana.

I don't like having both Spellskite and Stony Silence since there some matchups like twin where they have Spellskite wich makes you want Stony Silence but just can't because of your own copies. You are already transforming onto jeskai control after board wich makes opposing Spellskites worse.

If you want som ideas, i got i jeskai twin list here:

And you thought this was control?!

maybe Twisted Image to kill their Spellskite? (or a random dorck)

and Electrolyze is great in any ur deck. also Remand seems better then Mana Leak in twin for me.

American Twin is considered by far the weakest of the four Twin archetypes. Why no go with a more powerful and proven list like stock UR or Grixis? What does white really offer?

You need more sources in the main. I was able to play around Path to Exile with ease using a slower Temur Ascendancy deck with the following:

Typically what would happen is you would need to Path to Exile and then I could Remand it without fear because you only had 1x and no counters in hand. This happened in 2 out of 3 play-tests and in the third I finally gave up and mulliganed once getting lucky with two , one , and 2 sources.

Since you're playing Tri-Color ditch either a Steam Vents, Ghost Quarter or Desolate Lighthouse for Sacred Foundry or Hallowed Fountain.

My choice would be to leave the Steam Vents and ditch either a Ghost Quarter or Desolate Lighthouse for Sacred Foundry.

@NateJH: First off, as I said in the description, a list that was almost exactly identical to this just took down a GP, so it isn't really all that inferior. White gives me Resto and Wall of Omens, which are nice value cards. Most importantly, it also gives me Path to Exile which is the best removal in the format. I also personally think that UWR Twin is the best positioned to transition into a control deck post-sideboard.

@kengiczar: Thanks for the playtesting. I haven't done a lot of testing myself, and I know the mana base needs tweaking. I will probably eventually ditch the 2 Tectonic Edges for a Sacred Foundry and a Hallowed Fountain. I'll just have to find something else to throw in the sideboard against Tron. Any other thoughts besides the lands?

Against Tron you can cast Pithing Needle naming Karn Liberated. This stops T3 natural Karn. You already have Path to Exile vs Wurmcoil Engine.

Vs the T4 Ugin, the Spirit Dragon you can either Pithing Needle again or just counter it with a Counterflux.

After that you've had 5 turns to draw into your combo. You do still need to race them before they can get an Emrakul, the Aeons Torn and keep in mind that Oblivion Stone can destroy multiple Pithing Needles.

So to recap it doesn't work very well against Infect, Junk, Jund, Grixis Decks running lots of Kolaghan's Command (they usually all have 2+) or Bloom Titan.

Against Merfolk, Affinity, Podless Pod (A.K.A. CoCoPod), Faeries, Naya Goodstuff, Tron and non Twin decks it can be very annoying, to the point that it may be worth protecting with Remand if they have to kill it because you're stifling their main advantages.

Just be aware that Pithing Needle does nothing vs Mana abilities such as Qasali Pridemage and you have to be careful with Naya. There are 3 main archetypes and they all are very creature based: Naya Burn, Naya Aggro, and Naya Good Stuff. Typically the burn version won't have any Qasali Pridemage in the main but the Aggro versions will have 1-2 and the good stuff will usually have 2 because it's the slowest with stuff like Knight of the Reliquary and sideboard options like Kitchen Finks and other 3 drops.

Oh one thing I forgot to mention. If you run into Living End you can go into a Trinket Mage --> Grafdigger's Cage scenario. Obviously this isn't worth running if you can easily beat Living End. Even if you can't it's not exactly worth the slots unless you also know there are several Living End and Vengevine decks in your area. Also Rally the Ancestors combo decks will cry because of it. But again, none of this may be relevant and it requires a very heavy percentage of your meta to be running these decks to consider Grafdigger's Cage. (Cage also stomps on Goryo's Vengeance and Through the Breach btw : P )

Okay it got one GP win, UR and Grixis both have had many more results than URW. Even at the same GP two UR lists both got Top 8 as well. The URW's victory seems like an anomaly. Thoughts on why it is better than established Grixis and UR lists? Simply listing cards off as they are "good" isn't a good plan.

@kengiczar: that was actually extremely helpful and I really appreciate it. I was a little worried that I'd have trouble keeping up with some of the faster aggro decks, especially creature based ones. Do you think more board wipes like Pyroclasm would be an efficient use of SB space?

@NateJH: I think UWR is an interesting option for Twin because of what gives me access to. Having Restoration Angel and Wall of Omens, in addition to the typical Snapcaster Mage and Vendilion Clique gives me much more board presence than a typical UR shell. That can be a real advantage, especially with the current meta being so saturated with creature based strategies. It also gives me access to Path to Exile, which besides being the best removal in the format, is also particularly effective against Tron (Wurmcoil Engine) and CoCo/ decks (Voice of Resurgence, Kitchen Finks, etc.). Having also gives me access to better board wipes like Wrath of God or Supreme Verdict which are good against Jund. Finally, I really like UWR because I think it's better positioned to transition into a control shell post-sideboard, for all of the reasons mentioned above.

NateJH is, maybe he just wants to play it good enough for you? God it makes me sick when people jam the "this deck is better because people had success with it, blah blah blah" it's annoying. Somebody can win with anything given the proper plays are made, and their mistakes are minimal. But if you so badly want an answer, I will tell you why I like this list personally - more combo options, wall of omens is a great wall, path is the best removal spell in the format.

WUnd-R Twin powers, activate!