It was for me as DS either sleeps between DH & I or on the edge of the bed next to me and he would move about in his sleep, so the guardrail gives me peace of mind he won't fall out in his sleep. When he started crawling we taught him to get off the bed backwards & feet first so I didn't worry too much about him falling off when we woke up.

Having said that, he managed to get between the rail and the top of the bed one night in his sleep about a month ago - gave me a hell of a fright. I wedged pillows between the bed & my bedside table after that.

I guess it depends on how much your little one moves in their sleep and the drop from the bed to the ground - if it not too much maybe having cushions or something on the floor would be a better bet, 'cause all the rails I saw had stoppers and the one we got was the only one to go up to Queen size - it def wouldn't stretch to King