I'm winding up the first work week of using Ubuntu exclusively on my work machine. The back-story of my switch to 'Mountain Goat' is here
The experience has been nothing but pleasurable. There is very little difference between working on OS X and Ubuntu. This is good.
Of course there's a learning curve, keyboard shortcuts are different for one, and as I decided to not customize the out of the box interface and apps, there's been some learning there as well.
But learning new apps and work flow is fun and often rewarding. It challenges my brain and gets me thinking of new ways to manage things.
As you can imagine, I've received many offers of help and suggestions from the global Linux communities. I like this about Open Source. Yes, the Mac has also has a community vibe to it, but the vibe on Linux is more Punk Rock to OS X's Disco feel.