I agree with the try-and-buy, but it's a bit of a pain in the nether
regions, so I try to see what other folks have said to narrow my choices.
I never could much use for Caller ID on a headset since, unlike
Jar-Jar, I don't have eyes on stalks. On the other hand, I could see
some uses if I took it off while driving, since reaching for the Treo,
lodged safely 'neath the jacket/vest and seatbelt, is a bit problematic
at times, and sometimes I like to check who's calling before I answer.
A vibrator function can be useful on a headset small enough to stick
in a shirt pocket. The Jabra BT250v was the first I tried with a
vibrator; it was too large for convenient pocket storage and I think it
didn't vibrate-only, which I would have liked while wearing it.
I thought I'd run across a couple of headsets that would allow voice
dialing, but not with my 650.
Last number re-dial could be very handy, but I think the 650 didn't
support that, either, at least on the headset I tried.
The c|net review of the Plantronics 645 mentions it has a shirt
pocket carrying case and it vibrates on an incoming ring -- could be
useful on a headset that is meant to wear without an ear loop.
I also like having the earpiece in my ear, rather than on it or
beside it. I'm a little hard of hearing to start with, and in the Jeep
I'm practically deaf, phone-wise.
The Plantronic 655 (which superseded the 645) review mentions having
to raise one's voice a bit from time to time. That would be a deal
breaker for me, since I hate people who holler into their phones. I
really don't mind people talking in restaurants and airplanes -- just
talk as you would to the person sitting next to you.
Anyway, not I have a 680, and earphone technology has changed some,
so I guess it's time I started experimenting again.