For me the main reason is that it's Free Software, and to be honest, for most of the daily tasks I've been using the same free software on the mac already so there was no big clash when I moved to linux.

But I have one area where I wish I had a Mac (or Windows computer) and it's audio. Ardour is really great but all the work I had to get jack and pulse audio to kind of work together, jesus, I even bought special hardware so I wouldn't have to deal with this shit while recording my podcast.

I second your statement, the fun of figuring out how to do something with linux which I was able to do easaly on the Mac is quite far down on the list of the reasons why I use linux on my desktop.