I think the Squeezebox itself is very easy to use, but the slimserver software can be at times frustrating. For instance, trying to set up a playlist is not easy, when you want to freely add and delete songs/albums from the list. That is, compared to iTunes, which makes setting up a playlist child's play, slimserver is like getting a Master's in advanced "it doesn't make sense". You can use iTunes and then Slimserver will also use iTunes, but I want iTunes to have a highly compressed version of songs while Slimserver does not. I'm currently keeping iTunes and Slimserver separate.
The other thing you might want to do is set up your network using fixed IP addresses. While this typically is not a problem, when my computer reboots, sometimes my router will assign the IP addresses so that the music server no longer has the same IP address as it did before the reboot. This means that the Squeezboxes "lose" the server, and have to be reset. That's not a big deal, but sometimes it's a pain, when you have multiple Squeezeboxes.