We recently (in the last 3 months or so) switched to Chase Amazon for all our purchases from the Chase Freedom card. We make many purchases from Amazon so it just seemed more logical to use/get the points from there.
We have several other credit/store cards that we may use for one off purchases like Target card at Target, but 99% of our spending is on the Chase Amazon card now. In fact, a strategy I like to employ is to charge all our utilities, doctor bills, and whatever else I can pay with a credit card online to the Amazon card. We do have a few companies that charge for this option so we either write a check or draft from our Checking account, but most we are able to charge to the card.
It also means I typically pay one credit card a month for most everything in my budget, and we get many more point than we would just using it for day to day transactions.