I tend to thumbs up any deck that can beat me in Bronze, no matter what it is. I mean most of those players don't have access to every card, so I show them slack. If a fully upped deck can lose to an unupped deck, then they deserve the thumbs up.
I know I'm the minority and I'll be made fun of, but it's how I play.
From Silver-Platinum leagues, it's all in how they use their oracle card.
All: Ghostmare, firestall (not true fire decks), Mono Aether if the oracle card isn't an aether one, and anyone that packs 6 Steals/Deflags or worse, and Bh/EQ spammers.
If I've never seen the deck, or only once or twice, I'll rate it up if it was interesting and fun to play against.