I too was scared to start it....I didnt want him to get in the habit of waking every 3 hours. But..I finally did try it..and it worked amazingly! I just made sure that when I did it, I didnt say anything except shhh if he began to fuss etc...and kept little or no light on at all. He eventually slept through the night. It will top her up for the remainder of the night. Oh, and usually, he would just fall right back to sleep after eating--as though he was never disturbed at all.
Hope this helps..