"Cannot parse configuration file: the options configuration file contains an invalid line '{\rtf\ansi\ansicpg1252\cocoartf1343\cocoasubrtf160'.Only use key=value syntax"
...and then quits out of the launch process.
I'm running 10.10.1.
I really don't know, I am just guessing here. But the \rtf part makes me think of "rich text format". Are you 100% sure that you have saved the file as an ASCII text file, and not as a rich text file or something like that? Open a Terminal, go to the directory, and check the file type with "file":
~$ cd 'Library/Application Support/Bitcoin'
Bitcoin$ file bitcoin.conf
bitcoin.conf: ASCII text
(the bold marks what I typed)