@ Pro Design, I dunno maybe I was a little harsh on this Jazz out of the gate. With a few solid days of posing, transforming, and all around handling of the figure some of my reservations have faded.
My biggest initial down checks were the panels. That panel that doesn't want to tab on the right leg has been fixed. I didn't have mold flash like yours. It just turns out the tabs aren't stronger than the tightness of the hinge. Holding the panel firmly while trying to "fold" the rear windshield panel the opposite direction got it to lay flat/flush with the leg.
My other panel nitpick was the tabbing of the upper torso. Still not ideal, but making sure everything is properly aligned helps. Posing and transformation sessions also help. Turns out this figure actually needs a break in period for joints and hinges to function as intended.
Final nitpick is paint or lack thereof. Paint where applied is great. Paint not used where it could have been is a slight bummer. Downbeat doesn't need to drip with paint, but accents like those on the hood vents could go a long way.
The gray plastic. I don't hate it, and I actually think I know why they used it from a design stand point. Sure paint on the feet and shins would have been preferable. However, look at the abdomen. The sides are silver painted diecast and the center is the gray plastic. It blends fairly well for a region that will be shadowy anyways unless you have lights pointed UP at the figure. The gray shins could have been painted for sure. But then they wouldn't have matched the feet. And I'm pretty sure the feet weren't painted because they're attached via mushroom peg AND have a hinged heel. You paint the feet and due to their design you've now got paint wear, and a joint that will loosen over time.
To sum it up, I like Downbeat more after having time to digest it all. With no MP Jazz for the longest time the anticipation and expectation was too high. The figure is solid and looks great. The problem arose from where I personally set the bar. As a favorite toy and character as a kid it was hard to be objective.