I use it when baby is around 3weeks old. Actually it's my mother in law who wanted to use it, though I did not wanna start till she's older.
Till now, she's 3 month old. Still using it. It helps her sleep better so we no need carry whole day. Use it normally during day time as cot is quite hot n she can't sleep long. Night time will let her sleep in cot in air con room.
At first had a lot of worries using it. Scared not safe, or baby too used to it... But somehow I just did not wanna fight with my mother in law. She said can sleep longer, head shape will be nicer too. True enough, she had longer sleep, more well rested n growing well lohz.
But make sure the sarong is well tied. To be extra careful, can place mattress under the sarong (but I did not) as my friend had an experience when the whole thing fell out. But that's becoz her 10mth old too active and somehow wriggle her sarong off the hook. So I made sure I got extra rope to tie in case it came off the hook but will still remain hanged.