Quote:
I guess I was expecting 900MHz wireless POTS phone quality: base station in kitchen, phone .5 acres away in the back yard, clear signal.

The reception is pretty bad in your case but you have to remember that there is a significant battery size difference in your comparison. The Bluetooth headset + Treo both have to make do with a tiny Lithium Polymer/Ion battery whilst your 900MHz cordless phone has a mains powered base station and a significantly more chunky battery in the phone.