Just a few days back, if you remember, I had posted an older version of this theme which was full of bugs pertaining to text visibility. Here is the new version of the same theme updated today. When I used it on my Galaxy S2, I did not expect much from it. But it really surprised me! The imitation is so close that it gives you a pure Galaxy S experience. The theme has the puzzle lock and dialer from the Galaxy S and a beautiful weather clock widget from the Galaxy S3.
The theme comes in two variants: a black version and a white one. Personally, I prefer the black theme that is closer to native Samsung Galaxy UI.
Just copy the theme file to the MIUI>Theme folder, and apply from theme manager app. To show the weather on homescreen go to Edit Widgets, add Clock 2×4 widget by dragging it to HS, tap on the edit icon on the widget, select the Galaxy S3 clock weather widget from the preview image and apply. You will also need to install GenieWidget app for the weather configuration.