I have to applaud Peter on the original design, Mark on the final design, and everyone involved in the reveal for this set. This is the most that I've ever been hyped for a Lego purchase. The final product is a fantastic design, and I love the inclusion of the turtle, but the highlights for me are the green classic space men (and women!). Classic space was always my favorite growing up, but my core Lego years extended from the tail end of classic space through Blackron II, so I never had a space minifig in my favorite color, until now. I am definitely going to be buying multiples of this as soon as it's available. It looks like my spaceship, spaceship, SPACESHIP! is going to be getting a few new crew members.
As for the barrel arms, I think its a bit unfortunate that the initial image of the set focused on that detail. Seeing the set as a whole, they don't really stand out all that much to me. Honestly, the use of the pistols for the roll cage on the original design stands out to me more than the barrels in the final design. It was an ingenious use of parts to get the right angles, but I can't unsee two western style revolvers right in the middle of a space mech.
Finally, I just want to say that the comments from Mark Stafford at reddit have been a fascinating look at the design process, and I am impressed with the number of features that we're getting in the final set given the constraints of the project.