Although I've had my Palm Centro for a few months now, it still registers to me as the "new" cell phone.
I really liked the Treo 650 that I had for 2 1/2 years, but it did have a couple of annoying bugs. One was that the microphone voice software had some problem with it that it would only work for about 90 seconds, less in a noisy environment. After that, it would stop working in some wierd way and you couldn't hear it on the other end.
And unfortunately, the bluetooth in the Treo 650 didn't work very well either. You could use a headset, sometimes, but it was never capable of answering a call with the headset. And sometimes it wouldn't work at all. The Treo did work fine with a wired headset, and so I would always carry one for long conversations; I don't really like to have conversations with a cell phone pressed against my head anyway; the new smaller one's really aren't comfortable.
In a last bid to get a bluetooth headset that worked, I bought a Treo-branded bluetooth headset:
Unfortunately, this didn't pair with the Treo 650 any better, and so it sat in a drawer for a couple of years.
So...now along comes the Palm Centro that I bought a few months ago. First of all, it works fine as a hold-it-to-your-face phone. I've had 20 minute conversations on it, and it's fine. (Although it's battery life is lacking; that may be because the battery was old.)
Secondly, the Treo headset actually pairs just fine with the Centro:
What's really cool about all this is the convergence in the technologies. As it turns out, the Treo 650 and the Centro use the same power supply. Which means that I can use the old power supplies for the new phone, so I now have three power supplies for my phone, including the nifty travel one with the built-in plug adapters.
Furthermore, the sporty thing about the Treo headset (in addition to that it actually works with the Centro) is that it uses the same power supply as the phone, so I only have to bring one power supply when I travel (the light on indicates that it's charging).
One thing that's a little tricky about the Centro is that all of its functions are controlled by one button. To turn it on, hold down the button for about 5 seconds, and the light will flash a bunch of times, then flash every several seconds to indicate that it's on. When it's on, hold it down for several seconds, and it will flash several times to indicate that it's off (then stay dark). When it's on and paired with the phone, tap the button to initiate or answer a call.
The trick bit is to pair it with the phone for the first time. With the phone off, you have to hold the button down long enough for the phone to turn on, then continue holding it down until the light goes on steadily. This wasn't immediately obvious. In fact, thinking that my old headset didn't work, I bought another one on ebay (very cheaply). The guy sent me detailed e-mail instructions on pairing, which basically told me the above. Totally worth it, and I now have an extra headset.
Here's a brief video of setting the headset to pair mode (sorry I haven't had a chance to down-convert it; it's 4 MB).