I never heard of going online to buy it, but I suppose that makes sense. Most people just have the Schwan's driver come by every few weeks. My parents live in a rural area and the Schwan man would keep track of what they always order and even put it in their freezer when they weren't home. My parents would leave a note for any extras they wanted him to put there as well. They love it.
Schwan's food is usually quite good quality and has wonderful flavors. No it isn't the most gormet food in the world, but I've never known anyone to not like the food. The drawback is that it can be expensive.