Ahh, it seems that its rather simple.

I've decided to go for the default image from Raspberry PI website. The Raspbian Wheezy distribution.

Then after completing the installation, I just used 


    $ sudo apt-get update
    $ sudo apt-get install mono-runtime

Case closed, problem solved.

Btw. to move files back and forth, I've mounted a cifs folder, so when I place new compiled files from MonoStudio on the PC, I can just run it on the PI = maximum compile speed on Intel Core i7 @4600 mhz and still real hardware to run it on.

**BUG REMARK!**

Currently (february 2013) the current mono-runtime has some serious issues with DateTime because of hardfp. I havent tested this on softfp as I cant get the image to run after download, but the error with DateTime seems to be regarding the string output when formatting. You can still pull the bits and parts like Year, Day, Month, but the function to combine them into a "normal datetime string" will have to be a fix/patch of your own.

I'm currently not aware of other important bugs. But if I find any, I'll edit this answer again.

Happy coding people!