All Bluetooth headsets are not equal -- not just in price (from around ten bucks to nearly $200) and features, but also in terms of usability. Some of these differences may be absolute, some may be a matter of YMMV (Your Milage May Vary).

Things to look for

1. Uses a USB port (and cable) charging, nothing proprietary in the headset-side plug. The charging port on the headset must be a standard USB port (micro or mini). (The other end should be a standard USB plug, which lets you charge from a powered USB port on a desktop or notebook computer, or a USB charger.)

This reduces the number of cables or adapters you have in your travel kit and at your desk -- and means that if you forget or lose your cable, you can borrow one easily from somebody or pick one up affordably from any office/electronics store, or even from many convenience/drug stores.

2. Securable ear loop option. Or as I've dubbed it, "Ear-tenacity." I find that headsets that count on a snug fit into your ear to keep them in place as optimistic, especially if your head moves at all, like when you're walking down the street, up and down stairs, sprinting for a bus or subway or flight, or shaking your head as you disagree with somebody. I've lost at least one Bluetooth headset, not noticing it was gone until I'd clearly walked beyond where it popped out of my ear. So I prefer one that offers an over-the-ear loop, or whatever.

3. Sounding good (enough) to the other party. If your voice doesn't come through clearly, and extraneous sounds aren't filtered out, you need to keep looking. This is where you need a "testing buddy" you can call and talk with -- ideally somebody you can lend a headset to so you can hear the other-side experience. Your tests should include:

The moment is like the following experience, if anything, please discard the earphone, it has lost its function

a) Speaking in a normal voice or even softly enough that somebody more than arm's length away wouldn't hear. You shouldn't need to shout.

b) Walking down a noisy street; trains, lawnmowers, jackhammers, etc.

4. A minimum of parts and accessories. The charging cable needs to plug directly into the headset, not to some intermediary charging pod, and in general, the fewer components, the less to carry or lose. Similarly, the headset itself shouldn't disassemble easily, much less spontaneously.

5. Well-placed, usable controls. Remember, you're trying to control the headset by reaching up with a finger, without looking, to accept/hang up, change the volume, and maybe something else. You don't want to be hanging up on somebody when you're trying to change the volume. It may take getting used to -- or you may need different-sized fingers -- or a given headset may not be the one for you.

6. Comfort. You may end up wearing this all day, all week.

7. Findability. when you've dropped or misplaced it, a nice bright color would be good here. So would a "here I am" blink/beep signal, like cordless phones offer, activatable from your phone.

Useful but not essential features

1. Peer-to-Peer "walkie talkie mode" (i.e., talking directly with other headsets that are in-range.) I've read about this on some, like CallPod's Dragon V2 headset; it sounds like it could be useful, in some circumstances.

2. Simple voice control. I've now encountered at least two headsets that take simple voice commands like "Redial."

3. Multipoint (a.k.a. "multishifting") lets you switch it among several active devices, like between your BlackBerry and your netbook.

4. Small, compact USB charger. You want one that fits cleanly into a pocket or travel kit, but you're likely to have enough better ones kicking around; don't make this the deciding factor.