The Prius does have lots of room inside, that's it's main plus point in my opinion, apart from the eco credentials. But I actually think the Insight looks fairly spacious, too. Boot looks a similar size to that of the hatchback Civic, and there's a relatively flat floor for the middle rear passenger. Overall, I think Honda have done a good job here. Could've been more adventurous with the design though. Would've loved old-Insight-style rear wheel arch that covered nearly all of the wheel. The old model always reminded me of a Citroen from the rear. But with this one, they've still done a good job.
I've got an Aygo and a Meerkovonian meerkat :)