I tried my cousin's Ultimate 12 propel in North Carolina waters. I liked the natural 'pedalling-on-a-bike' feeling that reminded me of cycling on dry land; but to be honest, I didn't like doing so on my back at such a low angle. Then again, that's the same reason why I don't like the Hobie pedals. I'm a paddle control freak that likes to sit upright and avoid juggling my gonads in that fashion.
I would advise you to take a pass on the Ultimate pedal models, as the yak is akin to a canoe, and therefore, like a sit-in. The Mariner models are more similar to the SOTs that we use out here on the West Coast.
If it's a inside connection. you should ask to borrow it for a weekend and take it out to your favorite waters. There's no substitution for personal use.
Good Luck!