Rear visibility is definitely as issue in my hatchback. Removing the rear headrests does help some but my view angle is still rather narrow. Thankfully the side mirrors can be adjusted to make up for that to an extent.
As for the front seat, the padding on the bottom of the seat is a bit thin and I can feel it after just a few minutes in the car. The back of the seat is fine for me and I've long since gotten used to the angle of the headrest. I sit in a very upright position, too. Despite my gripes with the bottom cushion, I can't recall ever being sore after driving my car for even 8 or 9 hours in a stretch. Stiff, yes, but not sore.
I'm a little surprised that CR dinged the Sonic for back seat room. I have only ever gotten compliments from back seat passengers in my car due to it being surprisingly roomy, even from taller passengers who were reluctant to ride in it due to it being so tiny on the outside. I have a Cruze as a rental until my car is done in the shop and it looks to have the same amount of room on the interior, both front and back, as the Sonic despite being much larger on the outside. Sure, the interior is a bit nicer in many ways, but it doesn't feel any roomier than my Sonic and if anything, the front part of the Cruze feels a little more closed in due to the layout of the dashboard and console. I'll have to sit in the back seat for curiosity's sake before I return it.