Agree with deanishe and was thinking the same: cmd-return to open in Contacts. I didn't know of cmd-O until I found this thread. As the modifiers control and option offer other options, I think cmd is a good choice for perhaps the most often wanted other action.
IMO, it would be more intuitive if the "Open contact in Alfred/Contacts.app" feature worked like normal workflow results, i.e. ENTER for the default action and CMD+ENTER for the alternate.
It's a standard Alfred idiom to use CMD/CTRL/OPT/SHIFT+ENTER to perform alternate actions, while CMD+O is only used with contacts (AFAIK), so people are more likely to try CMD+ENTER, and to remember it.
Also, the subtitle should then change to "Open contact in Contacts.app" or "Open contact in Alfred" when CMD is held down (just as it changes to "Search for 'x' in Spotlight" when you hold down OPT when a contact is selected).
