pn03 is the only Mikami game I didn't play outside of his Disney output. I'm unsure whether that should change.
I really enjoyed it. So did Svejk. I think the way the game was advertised versus what it really is threw people off- it's not some Resident Evil-style game, it's a pure 'old-school' shooter, just done in 3D. You go from room to room shooting and dodging robot fire...that's it. It also has a cool atmosphere and an awesome soundtrack. It really clicked with me in an old-school arcade sort of way and that's probably what you feel find in reviews on it- the way it plays is pretty polarizing. I think a lot of the people who played this were expecting something more like what Vanquish ended up being, and this is not like that, from a game play standpoint, at all.
One thing I really liked is that going back and replaying stages will put the rooms you traverse in random order. Helps to make stage replays feel more varied. But the reason to do this is to basically grind for points to get upgraded suits. Once you get some certain suits or don't care about getting all the upgrades, there's no reason to go back and replay the levels to progress, but you can do it for speed/combo runs.
It sucks that this game bombed because I would have loved a sequel or next-gen HD port. At least it scales up really nicely on emulators.
I really think the way I feel about this game is the way Himu feels about Killer 7, but for different reasons. (PN03 and RE4 are my favorite Capcom Game Cube games easily.)