Ubuntu 14.04 works very well on my MacBookPro6,2. To check what version of mac you have:

sudo dmidecode -s system-product-name

Fans

I noticed it was running hot, then realised this might be because no fans were running. This can be easily fixed on 14.04 by just installing macfanctld:

sudo apt-get install macfanctld

Before that command had even finished running the fans span up and started to cool things down.

Function keys

By default the function keys do the "screen dim", "screen brighten" actions, and you have to use the fn key to get F1, F2 etc. I prefer to reverse this. Doing so requires pommed which again is included in standard 14.04 apt-repository:

sudo apt-get install pommed

Then a quick edit of the /etc/pommed.conf file to change fnmode from the default value of 1 to 2. After saving the changes to this file, apply them with a quick:

sudo service pommed restart

Screen goes black when on battery

Again edit /etc/pommed.conf to change …

    on_batt = 6

…to…

    on_batt = 0

…to disable this.