I suppose they were attempting to be more stylish; certainly not more realistic – the new icons are still somewhat cartoon suns and clouds.
What bothers me is that the new icons are actually less clear than the previous versions. If you’re using any screen resolution over 800×600, then the differences between “partly cloudy” and “mostly clear” are meaningless. One gray blob versus another? Please.
Yeah, yeah, I could just read the words. But in my opinion it’s poor design. Not that Weather.com is going to win any design awards 🙂