I did same work on my MBP.
like reply already there, it IS not much weight. very lighter than i thought. less than 50g. anyway it is work well even doesn't have an ODD, but problem happens when re-installing OS. i tried install boot camp-ed windows7, it was failed. i didn't tried OSX yet but i think it will failed either.
on the mac book produced with internal ODD(like regular MBP), boot camp installer can not run with USB memory stick. and as far as i know, there is no trick to do that(there is only one way, but its vmware virture ODD. difficult). you have to install windows by ODD. after then it works fine without any ODD.
so if you really want to remove your ODD, i suggest buy external USB ODD case for re-installing the os.