Almost... Getting the Plug to connect to my wireless network didn't seem to work: my network never showed and the Plug never indicated it was connected... After I removed the network cable, it still didn't report a WiFi-connection, but I was able to connect to it. So either the Plug is even more magical than I thought, or its a little buggy. Let's call it automagic.
So now I could start using my new gadget. I soon discovered that you always need to go through my.pogoplug.com to get to your files. I had read that this was the case when you want to access your files over the Internet when you're not at home, but it turns out you need my.pogoplug.com even when you're sitting next to your hard-disk. Two problems with that: (1) I don't want anyone between me an my files and (2) it's silly. Moreover, I found out that the printing feature works by sending email to email@example.com. Which has the same drawbacks.
To make matters worse, the Plug seemed to have corrupted my external hard-disk. This turns out to be a common problem with Pogoplug and NTFS-disks.
So, I needed to upgrade. Fortunately this is not a problem. There are many options, which all seem to boil down to Plugbox Linux and optware. It wasn't easy setting this up (partly due to hardware issues), but it's working now. I installed Samba and now the hard-disk connected to my Plug shows up as a separate drive in my file manager.
Next stop: printing