I recently did this through Harvey Norman, wish I'd looked into it better! We had just taken out a new home loan but needed a top up for renovations. We knew all figures we could borrow before we got the Interest free from Harvey Norman, got that little card and it brought our borrowing capacity down from an extra $50k to less that $10k (on top of our existing loan). I wouldn't do it again personally. We had to find the cash to pay out the interest free credit so that we could borrow money for the reno's. We also had problems getting them to send the first account so that we could actually pay it out in full!

Ive cancelled my card but think they send me stuff still offering to 'buy now pay later'.

ETA: My limit was also a measly $1500.