My wife and I ended up choosing the deceptively comfortable Söderhamn sofa. At first glance, its flat surface looks no more comfortable than a stack of books. However upon further inspection, which included the obligatory butt test, the Söderhamn is surprisingly soft and allows you sink back in its cushions due to its deep-set design.
We chose the 3 section sofa without the additional chase. It was delivered a couple days later and built on the day it was delivered (a recommended two-man job but was tackled by one eager woman without a hiccup).
If you're looking for a laid back couch for relaxing or entertaining I highly recommend the Söderhamn. To spice things up here are some other Ikea furniture that look great with the turquoise version of this couch: