Is anyone using the Airport Express' optical output to their 990? Is it convenient? How does your music sound? Is it really just as simple as configuring iTunes for my Lynksys wireless G broadband router and plugging in the Airport Express?

I don't use the express with my 990, it's in the bedroom connected to my Onkyo. The AE is very easy to configure. It can be used as a wireless router and/or as an itunes device. iTunes transmits to the AE using Apple's lossless codec, so there should be no degradation in sound quality. You can either use either a mini-toslink connector (digital) or a mini to rca (analog) converter. The new version of iTunes will broadcast to multiple AE's, so you could theoretically use them for whole house audio. The AE also has a usb port so you can relocate your printer or add a network printer. It's a very nifty device.