For me I think they are cool, if you can be getting some bitcoins for shopping online then it's really cool, cause you can be saving those money cays they are like free money and if you're lucky there might be a bull run and those pennies will turn out to become a huge amount of money more than you expected. That's a free money and it's cool. I only make use of Booking.com ,I know about Ali Express but I don't make use of it because I mainly use Amazon when I feel like to buy things online.