Any bad reviews on this product? Any things I should watch out for?

-Zak

A few people have reported their Blackberry's dropping the Bluetooth connection with the 640 after 15-20 minutes of standby.

Personally I've never had that problem with my 640. I love mine. It's the best fitting BT headset I've owned. And I've owned a lot.

I just got mine tonight from an ebay member for $79.99 shipped. Do most people use the battery to charge or actually use a car charger? Does it charge just as fast as a regular charger?

I use the plantronics USB adapter with my blackberry charger to charge my D640.

I love mine also, i had 3 other BT devices b4 and the 640 is by far the best in ever way. The longest it's gone without charging has been two days.
I even wore mine while blazing down the road on my motorcycle. I of course had to slow down to talk/hear but the fairing on the front helped keep the wind noise down. The ear piece stayed snug the entire time which is all i was testing to begin with.