They sting you by way of monthly account keeping fees. I'm not sure of the exact amounts but it's something crazy and there is no payment method that avoids it in most cases

Banks don't seem to like store credit cards. The amount if interest they have the POTENTIAL to charge is what the banks will look at as your potential liability for the card - so even if you have a $700 laptop on i, if you are approved for something more (3k for instance) you will be seen by financial institutions as potentially owing that amount plus interest (generally speaking, as much as 23%).

In my experience, you are better off just buying the cheap laptop and putting the money into your home loan savings later.