The osmo needs a forth axis to cancel the walking up and down movement for the camera. After owned the osmo for a week. All my footages look like I'm in a CS game walking mood...

You need to practice "the walk"!  There's a video on that in the tutorial section. There are also some quite clever DIY fourth axis solutions out there.  Keep practicing!

my osmo footage floats smoothly, its your walking. just dont extend your legs when you walk, put them close to each other, and don't hold osmo tight, i hold it a bit loose and trying to use my arm as a dual spring for steadycams haha, it worked for me