Seems to have worked for me except in the notification center where it reverts back to the original battery icon.
View attachment 342132
Strange... Try copying all of the files named 'WhiteOnBlackEtch...' and paste them somewhere different, but be sure to keep the Etch ones. Then rename them to 'WhiteOnBlackShade...' then copy and paste them back into the UIImages folder, so you should have 2x of all 5 of the images beginning with 'White' 5 should be named with 'Etch' and 5 named with 'Shade'.
Also has anybody found a fix for the battery looking squashed yet? If you look at the original image I posted the battery is taller and thinner, where as when we fix it for 5.1.1 it seems shorter and wider, and a lot harder too see the actual battery charge...?