Redirecting after submitting content - why this code doesn't work?
If you put a die in your MYMODULE_node_submit does it stop there after the form has been submitted? If it doesn't then your submit handler is not being called and you need to debug why that isn't happening. 

I just tried your code on one Drupal site I have with a good 40 or 50 modules and I could not get my additional submit handler to fire. Could not work out why.

I then put the same code on a testbed Drupal site I have with only the core modules installed and it worked straight away.

Once you've made sure that you additional submit handler is being called the you just need to put:

$form_state['redirect'] = '';


to redirect to the front page.