I have imported an png image with alpha to use as my HUD backdrop, after importing I check defer compression and save, there is no change to the image. In game and in the editor it still looks compressed. Also defer compression seems to be unchecking itself after saving, I have tried with TGA,PNG and PSD formats too with no luck.
I resolved this one by changing one of the other settings, namely the Filter to Nearest and compression to TC Vector Displacement.