The moment I heard someone was going to adapt One Piece into live action my morbid curiosity kicked in, fully expecting another embarrassment on the level of Dragon Ball: Evolution, but damn if they didn't succeed in faithfully recreating the look, tone and feel of the world.
spoiler
With the exception of one aspect: There have been ZERO dramatic closeups on crying characters' faces as they bawl their eyes out while streams of tears and snot run down their faces
The show fully embraces the wackiness of the original source material as opposed to early comic book/anime/video game adaptations that actively tried to sand down all the elements the makers deemed too weird and off-putting to the assumed general viewer. It's also sincere, and not soaked head to toe in constant shit-eating MCU-style sElf-aWaRE IrONY.
I'm two episodes in, and while I thought the first episode was pretty great from start to finish, I was a bit disappointed in the second one. Buggy's crew got really short-changed, with everyone with the exception of Cabaji just amounting to background characters and none of them getting to actually fight Luffy and crew. I was really looking forward to seeing Cabaji having a sword fight with Zoro while riding a unicycle after seeing how they nailed his design in the first episode. Instead he was just Zoro and Nami's jailer and got knocked out in one blow 
The fight with Buggy was also a bit underwhelming. Despite his powers he just mostly stayed in place whereas in the manga he was really mobile, flying and chasing people around with ease. I'm going to chalk that one up to the limitations of live action and hope thr members of the crew get to have more individual duels in future episodes.
I was a little disappointed with some of the things they cut - unicycle fight would have been amazing - but they did a pretty solid job of LOTRing it down to the important parts. All the actors do a fantastic job of capturing the over the top personalities without being clownish.
My one big critique is that the CGI gets very low quality in places, particularly explosions. Hoo boy are some of them baaaaaaad.
The bit with Buggy's head rolling around in an audience member's lap after Luffy knocked it off did look noticeably 2006. Probably should've put a cut in there and used some kind of traditional trick to show the head talking.
I think everything else has mostly looked pretty convincing so far though.
I'd say a majority of the CGI is done very well - particularly luffy's stretching - there's just the odd scene where it really stands out. Usually it's a background that looks too close or too far away, but either the end of the 4th episode or start of the 5th has one explosion in particular that is genuinely atrocious. Like 2003 stock explosion graphic bad. Ok, not quite that bad, but it has the vibes.
Its a real shame, because there are very few CGI failures otherwise (especially for a show with so much CGI), and everything else about it is so well done. Luffy's yell of defiance in the same scene as the explosion had me nearly crying with laughter, and later they get the CGI absolutely spot on for Dracule Mihawk.