I just got my 655 today. I am replacing my 640 because I want the DSP functionality. The 640 always sounded wonderful to me, but others could not hear me if there was a slight breeze or other background noise. I'm counting on the 655 to eliminate those problems.

One issue I had with the 655 is that it was missing the accessory bag that contains the additional ear gels (the small and the large one) and the ear hook. I need the larger gel. I bought this from one of the merchants on Amazon.com's website and received the headset within a couple of days. They claim they'll be sending me the missing parts, with no questions asked. Very impressive.

The 640 had a fairly loose fit in the charging sleeve, but that didn't seem to be a problem. The 655 has a very snug fit in the charging holste, and generally feels less flimsy.

Also, I had always noticed that the ear gel would wiggle on the 640 if it was left in the neutral position (the position you use to change ear gels). And it seemed to find its way to that neutral position quite often. So if you didn't twist it to one side or the other, it would not achieve a snug fit in your ear. My 655 is too new to comment, but if anyone has any problems with the fit, be sure to check that the pointy part of the ear gel is not pointing straight down the middle towards the mic.

One last comment - after enjoying my 640 for nearly a year, I found that the ear gel was beginning to disintegrate. Perhaps this comes from occasionally leaving it in my car, which gets hot during the warm months. But by now, the ear gel leaves gross little sticky pieces of rubber all over the place. Hoping that the new one will avoid this problem, but that may also have just been a sign of use, and time to replace the ear gels anyway...

And by the way, the 655 does not come with the metal case that the 640 came with, which holds all the accessories. And while the 655 does not include all the various charging accessories that the 640 did, I'm delighted that the 655 does come with the ONE adapter that the 640 did not - the usb adapter! I had to purchase that one separately for my 640, but it's included with the 655.

All in all, I'd say that the 655 is an excellent buy for anyone with a Blackberry or other phone that uses a usb charger (or anyone who has a usb port handy to supply a charge).