I'm 5'10" 155 lbs, size 10 feet and, once I got the outfitting dialed in, this boat fits me comfortably. Any boat that doesn't fit you isn't the right boat for you. Period. You might want the Diesel 60 if you're smaller, or the Diesel 80 if you are bigger.
I'm relatively new to whitewater kayaking and this has been the perfect boat for me to learn in. It has more volume (70 gals) than a lot of similar boats, and is very forgiving. It edges beautifully and predictably, doesn't ever seem to grab unexpectedly, floats up and over when some other boats want to nosedive, and rolls when I do what I'm supposed to do. If I end up upside-down, it's because I did something wrong. I've paddled my Diesel happily through places where better kayakers have flipped.
I'm not a terrain-park skier and I'm not a playboater. No interest in doing flips and spins and other tricks. I want to safely and comfortably enjoy the roller-coaster ride in Class II and some Class III. I do not aspire to Class IV and V, though I'm pretty sure the boat would do well for me if that was my goal.
I mostly paddle downriver, stopping to build skills like ferrying, eddying out, eddy peels and such whenever there's an interesting place to try it. Therefore, it doesn't bother me at all that this boat is less "playful" than some others. I'll take stable and predictable, thank you.
In short, I was looking for one whitewater boat I could learn in and not outgrow. The Diesel 70 fits me and what I want to do.