I am using my Treo 600 as a pager and have had no communications issues. The problem is that the built in MIDI tones are very low in volume compared to a decibel rattling pager. As MP3's are considerably louder, I have tried using those as alerts via Call Filter (only works on 600) which plays a designated MP3 via PTunes. The problem is that answering an SMS Page does not end the MP3 as answering a phone call does and the MP3 continues playing to its completion. Very embarrassing when you can't push a button to silence the pager and everybody turns around to see where the William Tell overture is originating from. Does anybody know if any of the 3rd party ringer programs (Ringo, Lightwave) have this problem?