I got so salty about the "one of G or B" type casting costs when I first saw them. I was still really primed for pre-modern creature power levels, and somehow these creatures that were *easier* to cast than something that takes only a specific type of mana were so much more powerful, and triggered effects off two colours of cards.
At this point I guess I intellectually know they are not completely overpowered but it's still hard for me not to see the early days of modern as a stupid power creep. Artifacts can be cost with any colour of mana, and you're making them *how* strong???