When I first saw it, I was surprised (I don't think anyone saw it coming), but my feeling was pretty much like
BWri's in thinking that, given all the Spirit Control material in mid-arc (including a reference to Gigantification), this would've sat better with Vegeta. I was fine with it, but that was about all.
Since then, I've come to view this scene at least partially through the lens of the Goku-Piccolo Daimao confrontation, like so:
Looking at it this way, the giant manifestation of Goku is a latter-day version of the appearance of the image of the Oozaru at the point of the decisive strike, giving Goku the opening he needs to land the final blow - only in the Moro arc, this is Divine Power, which is a special feature of the arc, as opposed to simply Goku's latent power, so Giant Monkey gets replaced with Giant Divine-Power Goku. Given the whole sequence is sparked off with Goku using the same line in both, it seems to me that this is what is the general point of the manifestation here.
Thinking of it this way, I enjoy it a good deal more than I did originally, as it plays on Moro's character inspiration from the Daimao to construct an ending to the battle that (in my opinion) deliberately trades on both this and the end of Dragon Ball (Vegeta's Spirit Fission intervention using Uub's Divine Power trades a lot, visually and conceptually, on the place of Genki Dama in the final battle against Buu), fusing features of the two into the climax of the arc. I think it works very well, naturally placing the demonic main villain in direct opposition to Goku and his story specifically (but then, I think there are several manoeuvres made to this end in the last Act of the arc generally).
I think the whole thing's clever, and I like it
a lot.
