I agree with old_school. These devices have made a big change in really enjoying everyday listening of music. Just hit a button and your off and running with all the music you have ever purchased. Oddly they seem to be a tuff sell to people who have never used them.
The usual question is why spend $300 on a device like an SB when you can get a 20GB player that needs no computer and fits in your pocket.
That's a good question... Once you can hook the portable up with a good digital connection and maybe the TV for a display, and have remote control, there won't really be a place for things like the SB. Another couple of years, I expect it will head that way.