Today I was on a conference call, on my Treo 650, as I often am (!), and I was going in and out of "mute", as I often do (!), and I noticed for the first time how horrible the Treo 650 GUI is for this.  Actually I've been dimly aware of it for a long time, but the horribleness suddenly shot into the foreground as I realized exactly how bad it was.  Now I'm a huge fan of the Treo 650, as you know, and in general the interface is very good.  But this is not good:

What we have here is a "Hang Up All" button - that's pretty obvious - and a "Cancel" button - pretty obvious also; I'm using a bluetooth headset, and clicking this button cancels the headset - then a "Swap" button - I had two calls attached, and can swap between them - and then finally a "Mute" button.  Aha, that mute button!  Take a close look at that.  Is it muted now, or not?

Since the Cancel button has a picture of headphones, and a little red X, you would think clicking the Cancel button would cancel the headphones.  And indeed it does.  Now the Mute button has a picture of a microphone, and a little red X, so does clicking the Mute button cancel the microphone?  NO!  In actuality Mute is already on in the picture above, and the microphone is off.  Clicking the Mute button cancels muting, and turns the microphone back on.  At that point the icon changes, like this:

I've had this phone for a while now, and I still have to think about this all the time ("is it muted now, or not?")  A red slash through the picture of the microphone like one of those European road signs would have been a good choice, that would indicate muting pretty unambiguously.  I Googled for "mute" and the very first hit was a great choice:

Totally unambiguous.  And cute besides.  Okay, you Treo designer people, are you listening?