[EDIT] The last version of MAMP with the last version of OSX Yosemite works fine.
I installed the beta of Yosemite two month ago, no problem with MAMP. With the last
Above solutions didn't work for me as I had no conflicting mysqld instances running. After check the mysql error logs in MAMP, it was obvious msqld was having all sorts of issues starting. The main error was:
[ERROR] /Applications/MAMP/Library/bin/mysqld: unknown option '--//skip-networking'
Which pointed me to an option in my.conf file. Somewhere along the line with debugging another issue I had added:
//skip-networking
As an option or I had commented it out. Removing that line allowed mysql in MAMP to start correctly.