I've installed some non-standard packages on the Mac and it was pretty tricky.

Not exactly 'move to applications'. And if some package is only available in source you're really in for a rough ride.

It's been a while though (about 2 years), possibly it's much easier now than it was then.

I use my mac so little now I've borrowed it to a friend here that does design. Too bad in a way because I really like the machine, it's so quiet compared to the pcs I use.

Well, that's exactly the thing... There's a vast difference between installing some library for a programming language versus an application that John Q. Enduser wants to use.

As far as installing things from source that also has improved greatly in the last two years as well, so there's that.

But in general I'd say the user experience when installing applications on the mac is certainly miles ahead of the way Windows typically works, and arguably better then even Linux (Ubuntu or similar) with the gui frontend to apt-get.

How do people find stuff ? Is there a repository of sorts ?

Well, there's http://www.apple.com/downloads/macosx/

Versiontracker.com and Macupdate.com are the two big ones for the Mac.