Mad Treasure was a decent villain, though it was mostly his powers and his design that carried him. The henchmen were pretty fun as well, even if Zoro and Sanji's fights with them kind of borrowed from earlier fights (vs Braham and vs Absalom, respectively). Only other nitpick-y complaints were that Chopper used Arm Point in the special, which was replaced by Kung Fu Point (at least I'm pretty sure about that), and that most of the traps seemed a little too convenient for each Strawhat's skills.
I had the same issues, though I felt the fights compared more strongly to Film Z's: Luffy has a fistfight with the main villain wearing chains across his chest while surrounded by boiling liquid, Zoro fights a female who lays traps and attacks from range then finishes without cutting her, and Sanji fights a ninja with a unique speech pattern (while Franky stays behind to fix the ship and makes a late entrance).
The traps felt a little cheesy to me too but the last trap made up for it. I was a bit annoyed Nami didn't have a chance to show off her own personal skills, like, say, reading the air currents during the second trap. Meanwhile, Robin probably would have been a lot more helpful than Usopp or Brook in propping open those jaws. And while I'm at it, Acier had no reason to blow up that last room since he'd never met Mad Treasure before.
Really though the big plot hole was how half the crew got captured. One of them implies they fell off the Sunny after the throat and were captured by Mad Treasure before the first island, but Franky on the second island acts like they had been taken there. I mean, the special made the most of them being captured, but the collars+slave courtesan outfits were really off-putting after pretty minimal fanservice up to that point.