Here is the meta breakdown for Gushfest (officially known as the April MTGO Power 9 Challenge). Data as usual was collected by Matt and me.
Congratulations to Rich Shay for taking down the event with Sylvan Mentor. Here are the top16 decklists: http://magic.wizards.com/en/articles/archive/mtgo-standings/vintage-premier-2016-05-01
Total Number of Players 60
Shops (Eldrazi, Martello)
Number of Players 4
Win Percentage 55%
Gush (Mentor, Delver, Grixis Pyromancer)
Number of Players 27
Win Percentage 50.3%
Big Blue (Blue Moon, BUG/Jeskai/Esper/Grixis Control, Grixis Tezz)
Number of Players 8
Win Percentage 50%
Dredge (traditional, pitch)
Number of Players 4
Win Percentage 50%
Oath (Omni, Oathstill, Oreo, Fenton)
Number of Players 4
Win Percentage 36.8%
Combo (DPS, Doomsday, Academy)
Number of Players 8
Win Percentage 59.2%
Other (BUG Fish, Dark Times, BUGstill, a deck with every 2 card combo in vintage)
Number of Players 4
Win Percentage 29.4%
No Show
Number of Players 1
Here are the archetype vs. archetype winrates, along with the sample sizes:
As the events title implies, a huge portion, 45.8%, of the meta was gush decks. Moreover, all but 2 of the decks we classified as gush were mentor decks (there was 1 doomsday deck that we classified as combo). There were only 4 dredge and 4 shops decks in this event, although they did post a reasonable 50% and 55% winrate respectively. Note that many of these archetype vs. archetype percentages are based on a small number of matches, especially those not involving a gush deck.
The severe drop in oath's winrate can likely be attributable to the huge drop in the number of shops pilots. See http://themanadrain.com/topic/82/mtgo-march-2016-power-9-challenge/2 to see the degree to which oath preyed on shops last month. Likewise, the winrate of combo can be attributed to this same drop in shops.
Although the metagame is quite imbalanced, I would hope that the impressive performances of dredge and shops against gush will entice more people back to those archetypes in the future.
EDIT: Here is a link to the spreadsheet since Brian posted it on Facebook: https://docs.google.com/spreadsheets/d/1WVt-ownFtxUTm-S9EH9eHCP4ba-rEnAIPhQHT9V9qlM/edit?usp=sharing