Unity 4.3+ lets you choose "png" format as part of the native 2d support. No more 16/24/32 bit uncompressed as the only lossless formats.
I'm not sure if the new "png" format would work for 3d textures though- there might be some other weirdness there (like maybe you can't turn on mipmaps or something) since it's supposed to be used for 2d sprites.
I'm not sure if the new "png" format would work for 3d textures though- there might be some other weirdness there (like maybe you can't turn on mipmaps or something) since it's supposed to be used for 2d sprites.