Great info from all of you - thanks! But as usual, I suspect I'm starting to overthink this, and just succeeding in making the decision harder...
Larry - I certainly appreciate your point re: ymmv, especially regarding fit and comfort. Ears certainly vary from person to person, and coming up with a universally comfortable fit is virtually impossible. You also caught my attention re: Plantronics not supporting call waiting on the headset - I would find that *very* annoying! Ideally, I'd like the phone in my pocket or its case - where I don't have to bother with it when I'm using a BT headset: I shouldn't have to fumble for the phone when I hear a call waiting signal! Excellent point.
Not sure what to think about the Z9 at this point - but egale's post certainly makes we wonder, although it's conceivable that a dud may come off the assembly for any product. But I'm wary now about this.
dtboos' post about the Nextlink Invisio B3 mirrors what I've read from a few others, although I can't find any real reviews on this yet. Their "soft spring" looks like a neat idea - I wonder how it would feel after an hour or two? When I looked at their website, confusing the issue is the fact that they have two new very neat looking headsets coming out later this year: the Invisio G5 and the Invisio Q7, both of which look extremely promising. See:
INVISIO Q7
The Q7 looks like it may have all the audio benefits that you might expect from the Jawbone or Z9, but what appears to be greater concern for comfort and fit. (EDIT: I just read on one site that the Q7 *is* an upgrade to the Jawbone - and that Invisio made the Jawbone for Aliph??? see:
Cellphones: Invisio Q7 Bluetooth Headset With Jaw-Sensing Technology - Gizmodo
Then I found that it seems that production of the G5 and Q7 was delayed a year. Impact Wireless is taking pre-orders for the products with anticipated release next month...see:
Impact Wireless)
The G5 appears to be incredibly small, but with the same "soft spring" fit.
What to do? I'm finding that I avoid using the Jawbone except for car trips where I know I'll need to be on the phone - it's that annoying. My Cardo Scala is simply disappointing and somewhat mediocre. My HS850 has mediocre volume and lousy noise resistance - especially since it doesn't use an in-ear earpiece. So I'm ripe for a new headset.
Sometimes I think it would be better to know *less*...