[Toucan]

Cmd-O has opened files and applications alike since I can remember (OS 6.) It's no more/less sensible than Windows, just different.

[kristiandupont]

I would argue in this instance that open is a more common action than rename and thus belongs to the enter key.

[sid0]

Plus every terminal (including on Mac) and every other OS uses Enter to execute a command or program.

Edit: wow, downvoted for expressing a fact. Stay classy.