Finished watching yesterday. My biggest gripe possibly is that live action adaptations are simply not for me ? All along I kinda felt disconnected and could never quite experience the series as a separate work, always mentally comparing with what I enjoy in the manga format. Which does not do it justice, as some things just don't translate well in a realistic motion picture. Fishmen, Luffy's over-the-top facial expressions, hair color... Negative points also for the overdone color filters. Too much gray on marine ship scenes, bleached colors on some occasions. It could have been more vivid.
There are some good elements, mind. All the winks and easter eggs (pretty sure I missed half of them), the Nami-Zoro-Sanji dynamic which carries the crew on screen, Buggy and Arlong, some well-made locations that really bring the One Piece world to life...
However, Luffy and Garp were never quite there for me. The only time Garp felt true to himself was when he angrily threw a canonball at the Merry then laughed at their escape, plus that curry house side comment by Borsalino. Otherwise he felt too serious on most occasions. I did not mind seeing more of Garp (and Coby), but it was not the character I had in my mind and I was never able to distanciate myself enough from the source material to tell whether his part the the story is genuinely interesting.
As for Luffy...At times he didn't feel carefree enough and there were only a very few scenes where I felt immersed, but I'm not sure the fault lies with Inaki. Mainly I guess manga Luffy is etched too strongly in my mind for any flesh and blood person to act as a convincing substitute.