Plus you have the flexibility of the swivel.
Not to mention glare and all the other problems you get if you are looking at it from an angle.

there's always that small percentage when you may need it
That's true. I find that there are some apps that are not designed for the landscape on iPad 2 (or iPhone, iPod touch for that matter) like Skype for example. It's always better to have the freedom which the swivel mount gives you. In the video it looked sweet n all but not practical.