For the past few weeks, we had this new kid in the block that somewhat mimics Delver Tempo of last season to a certain extent - UWR Midrange (or Tempo in some cases). It first originated from Harunobu Takeda in a LMC Championship and has experienced decent success ever since.
As the meta develops further into more control/midrange-oriented, some builds developed a lower curve by eschewing the red. There was less need for the burn suite due to the declining aggro decks in the meta, and it also allowed them to go for a lower curve after cutting Thundermaw Hellkite.
UW Flash, aka UW Tempo (or some would still refer it to UW Midrange), has a much lower curve than its UWR counterpart. While it has less versatile tools to utilize, it does gain consistency due to less enter-the-battlefield-tapped lands and a better manabase.
An Esper variant is also possible.
A few explanations for this archetype's recent success.
1) Cards like Geist of Saint Traft's power levels are undeniable, especially in such a shell that can protect him so well. By itself, it also effectively blanks most of the common removal spells in the format (especially those of Jund's) due to his hexproof ability.
2) It can deal with the commonly played Thragtusk decks rather effectively. This is because:
a) It probably is one of the few archetypes that play the most countermagic, which remains the best solution against Thragtusk decks that don't play Cavern of Souls.
b) It plays a healthy amount of evasive creatures that Thragtusk and his ground critter friends can never block.
c) Runechanter's Pike ensures huge amounts of damage can be dealt, neutralizing the life-gain from Thragtusk. Furthermore, the first strike provided by Runechanter's Pike would mean that your opponents would obtain even less value from Thragtusk combat trades.
3) It is more proactive than a control deck, playing more threats and less control elements. This would mean that it can beat other control decks if they take too long to setup, and that it won't fold to Slaughter Games like some control decks do (due to having too few win conditions).
4) Countermagic is ironically big in this meta, despite Cavern of Souls in the format. They remain the most effective generic solution against threats like Thragtusk and Olivia Voldaren among others, as well as against Planeswalkers. Dissipate and Syncopate are also effective answers to reanimator strategies.
Historically countermagic has been rarely good in aggro matchups. All thanks to Thragtusk and his pals which punishes aggro and encouraging midrange/control decks, it is now more justifiable to be playing with countermagic.
Not to mention Cavern of Souls is less played these days.
5) It can still transform into a control deck (albeit weaker) against aggro decks. The combinations of Pillar of Flame, Supreme Verdict, Detention Sphere, Searing Spear, Azorius Charm and Snapcaster Mage is an anti-aggro suite itself.
Not to mention that aggro decks are actually on the decline.
So one may ask, how is this different from control if they run pretty much the same tools? Well it may be difficult for some to understand if they are new to the game, but the short and simple answer is that they would use the same tools to further different approaches. For example, both UWx Tempo/Midrange and UWx Control often tends to use a card like Azorius Charm.
UWx Tempo tends to appreciate the Lifelink option and the bounce option a lot better, since it allows them to maintain board superiority and to race better. However UWx Control would rather utilize the card draw and the bounce option instead, since they would want to dig for more answers, stabilize the board and occasionally trigger miracle spells like Terminus.
Well this is a pretty long premier already and I do hope that most of you have understood this archetype a lot better. Regardless, do share your opinions/lists/experience and tournament reports with this archetype.