I had a hard time finding reliable information, so here's my experience after a recent purchase . . .
When using the Klipsch Image S4i headset with a Droid Incredible (with Froyo), the headphones work great (and sound quite good, I think), and the mic works as it's supposed to. The clarity on the mic is pretty good, at least in a fairly quiet room, even though it hangs below your neck. I haven't tested the mic with a noisy background, but I expect it to pick up background noise based on my experience thus far.
I have not been able to get the volume controls to work with any application.
The center button is supposed to pause songs with one click, advance to the next track with two clicks and go to the previous track with three clicks. In my experience this functionality sort of works with one media application at a time - the last one you installed.
The most recent media application I installed was Winamp. Using Winamp, one click pauses the song and two, three or more clicks will advance to the next track. I can't find any combination of clicks that go back one track. If you're using any other application and click the middle button, the last track in Winamp begins playing. I've tried the stock player, Mixzing, Meridian, Pandora, etc.
So I deleted Winamp just to see what would happen. I got the same behavior using Meridian, which is the media application I installed prior to Winamp. So I reinstalled Winamp, and the center button then controlled Winamp the way it did before.
If you're looking for a good headset with a mic, it might suit your needs. If you're looking for all the functionality the S4i has on an iPhone, you won't find it with a Droid in my experience.