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.