I voted for 75%. I know that I am definitely in the minority. However, I almost exclusively play IRL, and my wife and I definitely prefer playing with Colonies. If the layout is specifically a Province layout, then we will play a game with just Provinces, but then we always also try it with Colonies. I understand the restriction in the rules for Prosperity as to when to include Colonies. And if you don't have it as an expansion, then obviously you can't play Colony games. However, I think almost all games are better with Colonies and Platinums. I really love the added dimensions that come with them in the game. My wife and I don't mind the longer time that the games usually take.
I realize that many of you play mostly online. Perhaps the quicker games are better for that type of play. However, I really don't get a kick out of how few turns I can take to end a game. I like to be able to explore the options each different kingdom provides, rather than just focus on one or two cards and big money. Having Colonies allows for that to happen more often, and we find that to be a much more satifying way to play.