According to this review[1] it won't be useful for the Google Chromecast: "Internally, the hardware supports 2.4GHz Wi-Fi 802.11, which isn't quite as nice as the dual-band Wi-Fi offered on Roku's Streaming Stick."
[1] http://reviews.cnet.com/digital-media-receivers/google-chrom...
But it's not the bitrate that matters so much -- it'll work perfect for 20 minutes, and then completely fail for 2, then come back perfectly again.
I think the issue with my wireless is I'm in the middle of Manhattan and there are 40 wi-fi networks I can see, so it's already a little tricky. But whenever I turn on my microwave, transmission completely drops. So it's basically anytime I or any neighbor in five directions turns on their microwave.
5ghz channel sounds like a great idea, unfortunately I can't figure out from any manuals or docs whether my Zeppelin Air supports 5ghz or not -- the official specifications and manual just say "supports Wi-Fi". [Edit: Googling forums suggests it only supports "g", not "n". So, no dice. Oh well.]
That said, I don't know what's going on with your Airplay's music streaming, but the bitrate of music is far below Netflix's. It shouldn't matter much though, I stream my desktop in nearly lagless 1080p to my MBP via Splashtop. The compression isn't really that bad.