This article seems kind of vague. I have to call into question why they bother mentioning FLAC in this article. It says that the airport requires that you stream it Apple Lossless files. So how is it they make any comparison to FLAC, or any other kind of lossless codec?
Unless you have a very old pc I don't really think the cpu utilization of any of the lossless codecs is a big deal. I'm running an athlon xp1900+ and .APE only uses about 7% of the CPU compared to MP3 using about 3-4%. Consider also that my chip is over 2 years old, coming up on 3 years old actually.
When i read that earlier, i thought the article also try to proof that AAC can be transcode into ALE cheaply. That is why Apple chose to use it instead of FLAC. It's not any faster than FLAC by itself.