Apple just announced their AirportExpress. This little device is a 802.11b/g base station. The really cool thing about it is that it can stream music from iTunes directly to a stereo wirelessly.
I have read some posts where people like them. I just don't see myself buying one. I think that it would have been so much better if it had a little lcd or video out.
Since this requires iTunes to be running, and in order for someone to change what is playing though this device, they need to use their iTunes interface, most people will put their computer near their stereo. As soon as you do this, you might as well just use an audio cable between your mac and your stereo.
I definitly think that it is great if you don't already have a Access Point. Also if you need to extend the range of your current wireless network with WDS, I could see buying this. I am am happy with my TiVo with the Digital Music Player to access my music.