if you mean from the flat minimalistic style (one that came after steam community was added), yes, they changed from that.
they went and mac'd it up for all the pc users, but added a few useful new functions, I guess.
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friends are a big thing now, which is hit or miss, but achievements are more easily trackable without having to open up something new. the library shows more info for games (news from a few sites, gameplay hours, friends who are playing/own the game and achievements, and a few other links on the side) but that can be changed back to the old list-style if its a bother. the top tabs can't be, though ( Q.Q )
and the in-game overlay... takes up a good chunk of the screen with your friends and achievements... which I guess isn't bad if you don't use the overlay or whatever.
the store got a makeover too if you haven't seen it, it more or less matches the rest of the theme.
I hate it, but I guess there's some good in it. I just wish there was an option to use the old skin, or at least get rid of those huge tabs at the top/minimize the crap in the in-game overlay :/ (I swear I noticed some function that was taken out, but I can't think about it right now @_@ )
what has science done?