The door weighs about 40-50 lbs and after you remove the door you have to turn around and lift it over the seats in front of you. I've seen many people in the exit rows that I'd doubt are physically capable of doing it. All this while in a cramped space crouched over under the overhead bins. When the door handle is released, it simply falls in on you so you have to stand in a certain way and hold the door handles a certain way so you don't get crushed by it. Having never done it before, you'd think it's a lot easier than it is (yes I will admit that I had my lower hand placed wrong until corrected) Once you've done it in person I'd consider it to be an easy task though one I hope never have to perform. Keep in mind, on this tour we only placed the door on the seat next to us and did not have to lift it over the seat and out of the way.
This is a typical overwing plug door after it has been removed.
http://www.flickr.com/photos/olton_hall/1464978897/

One of the other people on the tour who opened the exit was a small women so size isn't an issue. IIRC she did comment that it weighed a lot more than she had expected. You just need to perform the required tasks quickly in an emergency.