Why MIUI did not redefined its launcher...This is difficult to report as there isn't anything to report. We hope for optimization to get better for the patchrom devices.
And one more thing. in 2.5.11 built, whatever theme you apply. Before unlocking the screen, default theme wallpaper flashes and then it shows the applied theme wallpaper which is very annoying...I'm not aware of any plans for an app drawer.