Good experience so far after more than a year. It is working as advertised. The payments/balance is a bit complicated as it shows your available money as e.g. "-$9.00". I am never sure if I owe money, or if the balance is actually in the positive (currently this is the case when there is a minus sign before the amount). However, this service requires a lot of trust and I am not so sure about it sometimes (e.g. who has access to my post and is it safe?).
A nice idea but... The app as well as the site is clearly still in beta. The customer service is sub optimal and you are likely to find charges you didn't expect or agree to billed to your credit card.
Communication may or can make difference