How does the 17x compare to the 16x lens? Can you get a more narrow dof?

Less chromatic aberration (CA), 10% wider field of view at full wide angle, SLIGHTLY shorter maximum telephoto range (mitigated by a more useable zoom range due to CA ).

Depth of field is a function of focal length, focal distance, aperture and imager size so the 17x lens has ZERO difference on depth of field (UNLESS you consider that it is more useable at several lens settings that may help to control DOF - full telephoto wide open is more useable in terms of CA on the 17x than the 16x)

But without factoring QUALITY of image into the equation, the 17x won't give you any shallower depth of field than the 16x.

After 3 1/2 years with the 16x I just bought a 17x for my HD100
- it's just a better lens, sharper, with better contrast and less flarey. Also a teeny bit wider, like taking one step backwards so that's helpful too. Switching modes HD looks noticeably more "HD" than before and SD, which most of my work is - looks better too but the difference in detail is greater in HD.

As far as depth of field is concerned that is determined solely by the combination of focal length and aperture, so no real change there - all lenses in this focal range will produce similar results.

I think it really should have been the standard lens for these cameras - but the 16x allowed JVC to provide an on the shoulder manual lens camera for around the price of a upper end all-in-one camcorder. I imagine using the 17x as standard would have blown the price-point, kinda like the 100's coming with the silly little battery rather than the V-mount or Anton adapter as standard.

addition - oh yes, less CA and vertical shading too