I've been using a Chameleon 2001 headset for the past month or so.
Overall, it's done pretty well. I'm using it for a cellphone and my home cordless phones.
The cellphone (Motorola V635) has a built-in headset 2.5 mm headset jack. The 2001 headset works fine with it, but the phone's not so good for the headset. You can't adjust the transmission volume, which means you sound REALLY LOUD when using the phone. Also, because the transmit is so high, while the noise canceling microphone tunes out a lot of stuff, even the stuff that's muted gets sent through quite audibly. Not great. In addition, I found the cord of the headset acted as an antenna for the phone, so there was an audible hum on the line until I removed the antenna from the phone.
I'm told by others in the know that this is a problem with corded headsets and digital phones. If you have an analog cellphone (a rarity in these days), you won't likely have that problem. I suppose this is why most digital phones are bluetooth enabled...
Anyway, I attribute the problems more to the phone than the headset.
I also use the headset on a couple of cordless phones I have at home and there, it performs flawlessly. The microphone's better than what's on the phones. One of my callers noted that my voice sounded clearer and had more bass to it when I put the headset on compared to when I was using the handset alone.
I suggest though if you're going to use a headset on a cordless phone that you get a cordless phone with a good range of volume adjustment. The VTech cordless phone I has the low volume setting rather high, even at the lowest setting. Sometimes it's necessary to move the headset a little bit off the ear when speaking to a loud caller. On my GE cordless phone, I just lower the volume and no headset adjustments are necessary.
In short, the headset works fine. The locking quick disconnect on the cord stays put as it should, even when my daughter's pulling on it with all of her might, so that's a neat feature. It's durable, having gone from the car dashboard to the floor several times as well as being stepped on my my daughter a couple of times (the microphone boom only, fortunately - not the speaker).
I use a cordless headset at work, so I don't use the Chameleon there, but in the home environment, which is sometimes more hectic than work, it's performing very well.
So well in fact that my wife wants one too.
Get your Chameleon 2001 headset by clicking here.