I'd say I'm most impressed by the compression. Being able to compress an image 42x is huge for portable devices or bad internet connectivity (or both!).
4*16*24*24*4 = 147,456
vs (removing the alpha channel as it's unused here)
3*3*1024*1024 = 9,437,184
Or 1/64 raw size, assuming I haven't fucked up the math/understanding somewhere (very possible at the moment).