I enabled Google result page's shortkeys, so when searching for something, in the result page, pressing down arrow on my keyboard would make the pointer arrow to point to the first result, and that arrow can be moved up & down using arrow keys. If you have shortkeys enabled in Google's settings, you'd know what I'm talking about.
Before upgrading to Mac OSX Yosemite, I always used Cmd+Enter to open links that the arrow is pointing at, but this stopped working right after I upgraded to Yosemite - nothing happens when I press the key combination.
I just tested this as well: in stackoverflow.com, press tab to select something, and when pressing Cmd+Enter, it doesn't open. But I used this key comb to open selected links in new tabs all the time.