Actually, there's a much shorter (measuring lines of code) and "more supported" (meaning there's an API) way:

+(NSImage *) imageFromCIImage:(CIImage *)ciImage
{
NSImage *image = [[[NSImage alloc] initWithSize:NSMakeSize([ciImage extent].size.width, [ciImage extent].size.height)] autorelease];

[image addRepresentation:[NSCIImageRep imageRepWithCIImage:ciImage]];

return image;
}