I have the Ariat Barnyard boots with side zip.  Although they are comfortable, after 155 miles of a 3 day endurance ride, along with quite a bit of hand-walking, I had blisters.  A lot of people ride in tennis shoes in my sport, but I like the ankle support.  So I decided to try the Terrain's and I LOVE them.  Super comfortable, especially around the ankle. The footbed is actually quite nice too for a riding boot.

I've only ridden one 50 miler in them so far and didn't hand-walk quite as much as the other ride, but I think they are going to be much better.  Cute enough to wear out with a pair of jeans too.

Like other posters noted, they do run a little large.  I normally take a 9 1/2, but both my Barnyard and these Terrain's I wear a size 9.