I do not recommend to do it, unless you have your firewall scripts tested and up to date, and you be a paranoic reader of your logfiles, to react to them in case of problems.
Although the "security by obscurity" question, the virtual harassment of your server connected to internet 24x7 will be one step less from crackers, more commonly checked in port 80 than in another port.
I would recommend just to change it to another port, and additionally install something like vddos, and have a "recaptcha" to prevent robots and unknown people from testing your root password all the time.
Regards,
Netino