Can I assign F8 (the play/pause key) to launch Spotify instead of iTunes?

System Preferences > Keyboard > Services.

Somewhere in there I believe! Don't rely on me though!

You can create a keyboard shortcut with different keys doing:
System Pref > keyboard > application shortcuts.

Then adding a new one, application as spotify, and create your shortcut keys

 

Me neither confusing but it will be somewhere around there!

 

I don't think there's a OS X preference for this directly, but you can set any application to launch with Automator and Keyboard Shortcuts, (as AppleMacNerd said):

Stage 1 - Automator

-Run the 'Automator' application

-Choose 'Service' as the kind of thing you want to make.

-In the left-hand list, click on Utilities, then in the next column choose the 'Launch Application' item. (Edit: drag the Launch Application item from the list to the blank area on the right, or double click it in the list (in Utilities to do get the same result))

- In the right-hand area of the window, change the drop-down list next to 'Service receives' to 'no input'.

- In the 'Launch Application' settings box underneath, choose the application you want to launch from the drop-down list (in your case, Spotify).

Now Save as something logical ('Launch Spotify' for example)


Stage 2 - Keyboard Shortcuts
- Go to System Preferences, and then click the icon for the 'Keyboard' section

- Click the 'Keyboard Shortcuts' tab, and then click on 'Services' in the left-hand column.

-On the right-hand side, scroll down if necessary until you get to the 'General' subsection (click the triangle next to 'General' to reveal the list, if it's collapsed).

-You should see the service you just created in Automator, 'Launch Spotify' or whatever you called it. Click on it once to select it. You will see an 'add shortcut' button. Click the button.

- Now you can choose any key/combo that isn't already in use (though there are a lot!) to launch your service. You should test it to make sure it works, and be careful you don't use a keyboard combo that is already used in the Finder. Also make sure you're in the Finder when you use the shortcut if it isn't working. I use cmd+§ to launch Safari, for example.

Edit: (cmd+§ might not be helpful on a MB Air I guess)… If your chosen combo doesn't seem to work, you probably have a clash, try another key combo. cmd+shift+9 should work, for example.

 

Sorry! I missed something out… you need to drag the Launch Application item from the list to the blank area on the right, or double click it in the list (in Utilities).


It should look like this before you save it:


If you click the run button at the top, it should open Spotify.

 

Hmm, not sure. I would just try a few key combos until one sticks. It does seem like it can be a bit temperamental sometimes when you're first setting it.