I’m not sure if this had been posted previously.
I’ve been in gold for a while and the transition to platinum is coming up.
Based on the message boards it sounds like going to platinum is a nightmare.
How bad is the transition actually?
IDK about the transition but it will help you be a better deck builder and player 
I went to plat very recently, and I can say that a majority of decks aren’t that bad. It’s just a select few that will crush you unless you get incredibly lucky, the rewards more than make up for this though.
A piece of advice: their creatures will always be bigger, meaner and smell worse than yours, so get rid of them, control is key.
Prepare to fight Mersicide…ALOT
Also Killwind and Kilpher. Seems those three are about all I see.
They match you based on deck strength. So if you make a deck with a low mythic count you face off against weaker decks
As others have mentioned,
You play Mersicide… a lot!
They do seem to match by planeswalker level, but from what I’ve seen, deck content has no bearing on matchmaking.
This is not true – I have quite a few low / no mythic decks that I’ve run in Platinum and I play the same decks I would play with my stronger decks.
I lost about 10% for the first couple events and then I was fine.
Be prepared to use a lot of control and play against a lot of control. You’re going to get crushed, mooned and engulfed every other turn with Tutelage in play if you go against a blue deck.
Koth decks will drop 2 huge haste creatures on every turn.
Mono green will contain Gaea.
Make sure your control game is tight and consider joining a community of coalitions where you have lots of people to support you.
My experience from recently making the transition is that I suddenly had to get used to occasionally losing. Not consistently getting crushed. Just, in gold most games felt winnable. In plat, every once in a while I throw up my hands and say, “Well, that happened.”
It’s harder to get placement rewards, especially given the first-come first-served model they have now. But I think on balance the improved progression rewards make up for it.
This is pretty much the meta in Gold already.