After waiting for over a year, I finally saw it just now. My god, Goemon is AMAZING. It's a shame there hasn't been word on this heading to the States.
Though, personally, I cannot compare Goemon with Casshern. Personally, for me, Casshern has been one of the top movies on my list that have revolutionized the way I thought about movies. It is one of the only films that I find as a great source of creative inspiration. But again, that's just my opinion.
But yeah, anyone else weary about seeing this film should ease up. I think everything that people were complaining about in Casshern (such as the overtly-philosophical plot and symbols and bad ending) are nonexistent in this film. Just be prepared that it's not an action movie, and that there is a bit of drama involved.